It's as if he was preparing to have amnesia. Also, how did the 'surgeon' manage to find it?
In his line of work it's a lot more likely that he was planning on dying rather than having amnesia someday. The implant was probably intended for his employer's benefit, not his own.
The 'surgeon' found the device when he pressed on the scar and noticed that there was something under the skin. It was a small device, but it would have to be big enough to feel if it contained a working laser and battery. Remember, Bourne had two bullet holes in him at the time, so it stands to reason that he'd get a thorough examination.
I personally think the implant of the laser was to reveal Bourns own identity to himself if any accident happens.
It was likely from the beginning that Bourne may get amnesia due to the drug effect. So if anything of that happens, he can get back his identity easily(Like the movie went on). Maybe they thought, it will create pain in the implanted area and he would eventually find it. But I guess, his employer did not think that after committing to the plan, he would turn against them.
The doctor found the laser because he wanted to examine an severely wounded body thoroughly. So he found the scar, felt something inside it and made it out.
Why did Jason Bourne put a laser with his bank account number in his body, it's as if he was preparing to have amnesia.
First of all, as a previous person said, in this type of work, they are more likely to prepare for dying rather than preparing for amnesia. In fact, in Supremacy, it is specifically made clear that no one other than Bourne has ever had amnesia. When Nicky Parsons, the person responsible for looking after the agent's mental health, was questioned, she said the agents had a bunch of problems due to their job, but when Pamela Landy asked if they also get amnesia, Nicky said "Before Bourne? No."
So the bank account laser was not created in preparation for an anticipated amnesia situation.
Why did Jason Bourne put a laser with his bank account number in his body?
That bank account was not his.
In other words, it was created for him but created by his employers. This is made abundantly clear in the first movie, Identity. When Bourne goes to Switzerland find the bank that the laser revealed, the bank staff not only notified the team at the CIA in America, he also told them exactly what Bourne took with him and what he left behind. This is revealed when, in the CIA office, one of the people said how "he" (Bourne) took everything except the gun. How does the bank staff know that? Because the bank staff has access to that special account and they could have checked what was still in the safe deposit box after Bourne left. The bank isn't working for Bourne, they are working for whoever set up the account for him to use on his jobs. Also, the CIA people already knew exactly what was in the safe deposit box which (again, being told that the only thing Bourne left behind was the gun) proves they were the ones that put it there. More evidence: the CIA are the ones who gave Bourne all his other passports (when he visits a country, they know he showed up on an alternate passport), which is why they were in the safe deposit box in the first place - they are the ones that made it and put it there.
So what was the laser for? One of the comments asks this:
Why would his employer need the information in the implant if the information is provided by the employer in the first place? It doesn't make sense.
It makes perfect sense.
As one of the comments said, the laser is like a microchip/dog-tag for all the agents as an identification tool. It is unlikely that Bourne is the only one that has one. Also, as previously mentioned, they are more likely to prepare for a dying/capture situation rather than an amnesia situation, so the laser allows the CIA authorities to identify the person if they were killed and the body was made unidentifiable (say, the face was badly burned).
Imagine this: If the person was captured, or killed, and the body was searched, the laser would inevitably be discovered, and relatively easily, as demonstrated by the surgeon on the boat. Considering the legal activities of the CIA is probably top secret, the fact that Treadstone (a program in the CIA which Bourne was brainwashed into participating) is an illegal program, the people of Treadstone would want the agent's information to be even more secretive and difficult to identify. So, rather than putting the person's identification information directly in the laser (which would easily be revealed to anyone who finds it), they put a bank account info in it without any names or other identifying info. THEN, even if the laser falls into the wrong hands, short of torturing the person (probably which is why the Asset in France chose to jump out the window instead of continuing fighting or walking out the door), the only people who have access to the information contained in that account, are the creators of the account (ie the CIA) and the person the account is made for (ie Bourne). Then, through the bank, they (the people at the CIA who set up the bank account) would be able to identify who the bank account belonged to/was made for and identify the otherwise unidentifiable person. A bank only gives information about an account to the authorised users and holders, in this case would be Bourne who uses it, and the CIA who set up the account.
how did the 'surgeon' manage to find it?
In Identity, after the fishermen fished the body out from the ocean and brought it onto the ship, they discovered the guy was still alive, so the surgeon looks at him to see if he could be helped (considering he was unconscious at the time, the surgeon could hardly ask him questions). This is just normal human response: In any normal circumstance, if you helped save someone, you would see if they are alive, and if so, do what you can to help (if not, they probably would have called the police but this was on a boat), which involves checking for injuries. You would want to check everything - is he breathing? Bleeding? Broken bones? Embedded foreign objects? Missing limbs? Other injuries? The surgeon in fact found the bullet holes and upon further investigation (again: it is normal to check everything - finding one injury doesn't exclude the possibility of other injuries) finds the laser in the guy's hip. This isn't so difficult because it was placed in a relatively superficial area. Just under the skin is an easy area to place something and is minor surgery as opposed to somewhere deep in the body which would require major exploratory surgery, so it made it easier for the surgeon to accidentally find it.
As for another question a commentor put:
why locate it in the one region he can't reach himself? In every other way, Bourne's been highly trained to be very independent.
Again, that laser was not made for Bourne, but for the CIA. In any normal circumstances, Bourne would have no need to access that because with an intact memory, he should be able to know where that bank is and why he needs to go there/what is in it. This is proved in Identity when he asked the bank staff how long has it been since he was last there, and the staff responds "3 weeks", meaning Bourne has been there before and without the assistance of the laser which, until now, had been in his hip and as said, inaccessible yet out of the way and un-obstructive.