im trying to determine why the wave track above the piano roll is moving when you hit undo.
im guessing this is because you have copied a piece in somewhere.
it may have been the point where I saw a pop up box in the corner out of site.you said:"saying im going to put this to beat 1 here ?"
if I saw the whole screen I may have known that.
sounds like this othr person here has a good idea though with what he has to work with.
I on the other hand, do not. (my bad I guess)
check your layers and it might even be worth scrolling all the way down the timline for your missing clip.
sorry and I do wish you the best with your problem.
good luck.