Indeed, what you say is so true...even if today, any dinosaurs or species once thought to be extinct were found alive, that would have no effect on ToE....we know that every so often, some living creature is found alive, that was thought to be extinct...and so just exactly how would that do anything to ToE...the answer is, it would not do one thing...if you understand that something is extinct, because it has not been seen for x number of years or decades, whatever, it winds up being called extinct..
But I am sure, that calling something extinct does not for sure, 100% completely sure, that it is extinct..what is means is that it is believed to be extinct...because the only way to declare something 100% extinct is to have every inch of the land(talking about land animals here), being inspected by one or another human at the same time...at that point, when no one at that time sees a particular living being, and we know every single inch of earth is being inspected at the same time, then we could say for a surety, that 100% something is extinct..
Why do people think that when something is called extinct, and then they find out they are not actually 100% completely extinct, that somehow does damage to ToE?...that is illogical at best...unless of course, one does not understand the ToE to begin with...
Well, it would if it were a prediction of the theory...not that I'm saying that it is mind you.
I have noticed though, that many of the articles posted here on this forum, concerning evolution, use the term "expectations."
We can be quite certain however that the huge clade which contains the dinos, aside from birds, is extinct. We could be wrong but that chance is quite small.
In any case it doesn't lend anything to creationists who through their arrogance believe a single sighting of a dinosaur would disprove all of the ToE and its many tenets.