Fair or Foul?

[Rufus]

We're playing USSSA rules and this happened in the game before us. A grounder is hit to the base of the picher's mound (we use portable mounds, but I think a real mound would change the rule - please correct if I'm wrong). It bounces off the front of the mound and:

1. The catcher fields it in fair territory, then throws the runner out at 1B (this is what happend in the game)
2. The catcher fields the ball in foul territory (i.e., it bounced from the mound to foul territory without contacting anyone/thing before the catcher picks it up in foul territory)

The umpires called the runner out in the game and I believe, based on previous threads I've read here, that is correct. What's the ruling in the second scenario? My understanding is that it's a foul ball but, when asked, the umpires last night said it would still be a fair ball since it contacted the mound in fair territory.

I seem to recall a thread here with a hypothetical example of a ball getting hit to the outfield with tremendous backspin and bouncing back foul between either 3B or 1B and home without contacting a fielder and it being a foul ball.

I looked through the USSSA rule book and couldn't find anything in terms of a definition of fair/foul ball. Incidentally, what's the best way to search through a rule book like that? I use a key word search but that never seems to work very well. Is it better to look through OBR since USSSA is based on those?