Here is a pretty interesting foul ball.
The more interesting question is what would happen if this was just a pitch that got lodged in the mask.
5.09 The ball becomes dead and runners advance one base, or return to their bases, without liability to be put out, when—
(g) A pitched ball lodges in the umpire’s or catcher’s mask or paraphernalia, and remains out of play, runners advance one base;
Again this is a foul ball so the rule does not apply. But, can you imagine a catcher whiffing on a pitch and the runners all getting an extra base. That would be a heck of a way to lose a game.
Balls lodged in player/umpire equipment is covered on page 61 of Rulegraphics.