I was playing a game last week and a notice came up saying "Your opponent is on vacation"  Which is totally acceptable, but when I checked the users other games I found that they were only on vacation in my game.  It has happened again today.  The whole idea of the vacation option is exactly that! A vacation from chess dot com,  a holiday.  Whoever changed the rules like this is an idiot.

Perhaps the time ran out out on that particular game, so it only kicked in for that game at the moment?

i think i have notice this as well in the past, although i was not sure if it was a glitch or whether it is actually possible to go on vacation for specific games. i have had opponents who were on "vacation" come online, make a few moves then leave all while on vacation. it might be a similar situation.

When you are on vacation, It only lists vacation on games where it is your move. Are you sure that it wasn't just the case that your opponent was only on move in your game?

I have a opponent who at the moment is on vacation in all his games, but his ratings have managed to go up. In his game against me , he is not in a very good position.

That could easily happen if one of his opponents resigned.

If I'm abroad on vacation, and I happen across an internet cafe, I don't just buy a coffee.