A few weeks ago we had a successful steal on a foul tip in a HS varsity game. Pitcher tried to send the runner back to first because "it was foul." Runner was ready to listen to the pitcher before I killed the play.
In a different game a catcher gunned down a runner attempting to steal on a foul tip. I complemented her on knowing the rule. It turned out that (1) she didn't know the rule, and (2) didn't realize that it had been a foul tip.