Poor play suddenly becoming excellent play

I've noticed that people tend to blame to many of their own deficiencies on their opponents using a prog. From what you have just said, it might just be that the person you played learned some opening moves, doesn't handle the middlegame very well, but has a knack for endgames, for example. I mean, of course the computer use cannot ever be completely excluded, but i don't think it's the case as often as some think. (I myself have been accused various times of cheating just because i played a good game and won against a (much) higher rated player - it goes without saying that i never cheat but I do play a decent game from time to time).

Are we talking blitz, standard, online? I guess it is more probable when the time settings are a day or more..
Without naming anyone surely you can produce a game that illustrates this?
BTW, I imagine people play a few book moves might drift a bit concentration wise in the middlegame, then on realising they're in trouble actually focus on the game.
That could be another reason why someones play might pick up.

I think it depends on the game too.
The hardest part in the game is mostly just right after the book moves where there is no concrete plan to overwhelm your opponent, so of course many inaccuracies happen here.
Later while Late midgame its often easier to find best moves with less pieces on board
In Endgame its often harder again.
So of course if somebody played very bad in the beginning and suddenly does 10 times the best move in very complicated positions he could be using a prog but why didnt he use it before?