People DO experience exactly what SaraBeth wrote about, happened to me as well. In Sonny's case he experienced really bad trauma. People in car accidents don't even realize they may have blacked out for a few moments. Many folks have said......"last thing I remember is.....and it is something that occurred long before whatever happened to them.
In my opinion, if Sonny does remember about Derrick, why in heaven's name would Sonny want to confront Will with a room full of people there. And why would he even want to do so, when he is very weak and tired from all that happened. The mugging, surgery, the reaction.....
He can see Will is very concerned, very worried, reluctant to leave his side.
I don't trust these writers.....
but I do think right now, Sonny doesn't remember. And if he does, then he will deal when he is stronger.