Sherlock's text to the victim's phone in “A Study in Pink”

Question

In S01E01 A Study in Pink, Sherlock discovers that the killer kept the victim's phone and decides to send a carefully crafted text message to it. He sends, "What happened at Lauriston Gardens? I must have blacked out". Along with an address and "please come".

Sherlock explains that the killer, after receiving such a text, must know that it could only have come from his victim.

Isn't this a really strange thing to do as a victim that woke up in a strange place without their phone and (apparently) their memory? Most people would assume the phone was lost and if anyone had it at all, they'd be a complete stranger. Why would you text such a thing to a stranger that found your phone?

One explanation could be that the victim thinks a friend must have grabbed their phone. But the victim in this episode was on a business trip, presumably traveling alone.

At this point in the story, Sherlock doesn't know the killer is intelligent. Does Sherlock purposely send a text that doesn't really make sense assuming the killer will panic and not think it through?

Answer 1

The victim just didn't leave (or forget) her phone. She actually planted it on the cab driver (then etched the password on floor with her finger nails).

While texting John asks Sherlock:

JOHN: The murderer ... You think the murderer has the phone?

SHERLOCK: Maybe she left it when she left her case. Maybe he took it from her for some reason. Either way, the balance of probability is the murderer has her phone.

Later, in the episode we come to know that Sherlock's theory of murderer having the phone is indeed proved right.

SHERLOCK: She’s cleverer than you lot and she’s dead. Do you see, do you get it? She didn’t lose her phone, she never lost it. She planted it on him. When she got out of the car, she knew that she was going to her death. She left the phone in order to lead us to her killer.

LESTRADE: But how?

SHERLOCK (stopping and staring at him): Wha...? What do you mean, how? Rachel!

Also, the cabbie has managed 4 murders and make them look like suicides. Sherlock knows that the murderer is intelligent. When John and Sherlock are heading towards the address to meet the cabbie, the following conversation takes place:

SHERLOCK: No – I think he’s brilliant enough. I love the brilliant ones. They’re always so desperate to get caught.

JOHN: Why?

SHERLOCK: Appreciation! Applause! At long last the spotlight. That’s the frailty of genius, John: it needs an audience.

Source: http://arianedevere.livejournal.com