The X-Wing Escort Card (Core, Block 12, 3/6) states that an opponent must sacrifice a vehicle unit under his control when [X-Wing Escort] exists play, as an interrupt.

Does this mean that if the opponent does not have a vehicle to sacrifice, the Escort cannot exit play? The interrupt would take place before the X-Wing Escort was allowed to exit play, correct? I.e. would it just stockpile damage infinitely? Or if there's no vehicle to sacrifice does it simply leave play with no penalty to the opponent?

Thanks. (Also I tried seaching the forums for an already existant answer, however I wasn't getting anything back on the search results… so I apologize if this has already been asked.)

It still leaves play. You may trigger the interrupt if you want. So no opponent vehicle? Nothing to lose. If your opponent does have a vehicle, you can still choose not to trigger the interrupt. I don't know why you wouldn't, but it is up to you if you want that interrupt to happen.

Agreed. The DS sacrificing a vehicle is not a pre requisite for X wing escort to leave the table. This is just an optional interrupt you have the option of triggering WHEN Escort leaves play.