As I said, my boss says "don't signal it when you throw the flag and the foul will bring it back." So, I don't.
And, FWIW, if I "think" I have a hold, I don't have a flag on the ground. That flag doesn't leave my belt unless I know damn good and well that I saw a foul. 
I understand what you mean about the bossman, but you misunderstood what I meant with "you think you have a hold." Certainly, you do not flag penalties that you "think" you have, but I'm sure you have been in the position where, for example, as a LJ, you see the defender fly across the NZ before the snap. Flag, offsides. The U, however, saw an offensive lineman commit a false start prior to the defender coming across the NZ. Accordingly, you thought you had a penalty for offsides, but the proper call is FS. Context is everything.
