That was one of the badly portrayed parts in the Sherlock episodes.
If you want to get into like a real reason for why Sherlock might have not seen the glass not being there is because he wouldn't have even expected the glass not being there. Eurus must have caught him off-guard.
If Sherlock had known something was up, he probably would have noticed that ...
Read about the method of loci.
Create a small 20 loci palace in your home, just one room is all for now. Then encode, and subsequently, attempt to remember 20 random objects.You will surprise yourself, guaranteed.
If you doubt it's efficacy and if you have the mettle, I'd recommend creating and testing a 100 palace loci and list.
Once you ...
I don't understand what investigation was meant to be done by Sherlock since he already knew about the terrorist attack and had a remedy for that?
Mycroft involved Sherlock to obtain the photos of the compromised royal person from Irene not in relation to the terrorist plot.
Sherlock only got involved with the Coventry plan because he had the phone and was ...