4. If you lost.
This is very upsetting and annoying, I know. Often this happens due to carelessness or a blunder. In such a case, it would be wiser (see point 3) to ask for an autosave. I don't like doing this myself, but sometimes I still ask for one. I never refuse.

There is a corresponding topic about autosaves at /topic/5676/; read it if you haven't already (especially newcomers). For example, when playing against me, I give one autosave, the second one with difficulty (unless you take it yourself after that), and the third one is unlikely (unless the game is really interesting). But in general, you need to know your opponent's personal attitude towards this matter because they may refuse an autosave, and you won't be able to make any claims. But usually, these issues are resolved normally ;)<