This is a known issue. See here  http://www.chess.com/forum/view/help-support/got-24hrs-added-to-my-time

Yes, known issue, but I doubt that chess.com will react.

This is one of the the membership features, and its even advertised(look at auto timeout protection):

http://www.chess.com/membership2.html?c=navbar

Recently they just change it to minimum 24 hours vacation, but fundamentally nothing has changed.

You can call upon "vacation abuse", but unless the game is "completely and hopelessly lost", there's nothing you can do.

http://support.chess.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=691&nav=0,6

I've seen games where an opponent was worse than in your game, and they're still not declared "completely and hopelessly lost", so I guess you will have to play a bit more.

Just save a expected line with conditional moves, this might help a bit.