I'd start looking for corpses inside of the wall. I mean, I got in this wall somehow, right? There must have been a reason, right? So, in the situation where I wake up inside a wall with no escape and no means of communication, I would assume that someone put me there for a reason....I must have pissed them off something fierce and, deducing from there, that this is probably a habit of theirs, seeing as how burying someone alive inside a wall would be perceived as a rational response to well, whateverthefuck it is that I must have done.
Anyhoo, I start looking for other corpses, sustain on whatever remaining nutrition that they provide, until a further solution can be determined.