I would assume in that case, if the person knew what they were doing, they would have removed the foil (though if they just cut the foil off the top they probably would have not seen it) they would have presented you the bottle and said "sir, this cork appears to have failed, would you like me to open it for you anyways?"

At that point I would think they would not charge you a corkage, just pick up the glasses and take them back. Once they open it however, I think the fee would be due them.

Did you have them open it? Seepage in and of itself is not the end of the world, it's possible the wine was still fine and just the stuff the pushed out was bad.