It wasn't that it was my job to watch the fair/foul ball. I simply saw it land a yard fair, and both F5 and R3 had blocked PU's view of the line.

Yes, you eat the blown foul call—in most cases. But if PU calls foul on a ball that actually hit the foul pole above the fence, that can be changed (I know that dead ball cases are different). And what about winning run on 3B in bottom of 7th and, let's say, 1 out? BR hits a line drive that lands obviously inside the LF line and then PU calls it foul. R3 scores. Do you still send him back and eat that one, too?

Yep

Easy to say. Actually sending the runner back to 3B on an <i>obvious</i> game-winning hit is something I don't think I'd do.

If you deny the hit, you will be responsible for a famous horrible call that everyone will always remember. If you reverse yourselves and let the run score, the defense will gripe but they and everybody else will know the game ended as it should have. With that choice, I'll take the right call and sleep a lot better.

Bob, is correct. As long as there is no other obvious damage to the bat. A dent is a dent, not a crease or a crack.