First, you should check your opponent's game history. If his opponents have a pattern of resigning at unusual times, then it could very well be something that he is causing.
If that doesn't turn up anything, then you could try to contact chess.com support staff and ask them about the situation directly.
I have been playing online chess using the app for my smartphone, an LG Optimus V. Today, I made a move in a great attacking position. Soon, I found that my game with my opponent was over. At first glance, I assumed that he resigned--which seemed a bit premature, but not out of the question.
However, it seems instead that I was marked as having resigned, and my opponent won. This is quite frustrating, since it was a rated game, and I felt the advantage was clearly mine. In no way did I possibly resign.
I noticed that when going into the "finished" game, if I attempt to back out using the back key on my phone, an altogether wierd and unrelated position will pop up. I also noticed that some type of position setup moves had been entered--at least that is what it appears to be.
Is there some bug in the app, or maybe someone has found a way to resign opponents? Is there someone I can complain to?
"Desolationrow"