I know that if you do anything to update your playernamehere.c4p then you keep any exp you have gained or feel the effects of any exp lost (dieing). If you were playing on multiplayer, if someone joins or leaves, your playernamehere.c4p updates (I think it does, anyway). there is a message in the chat that says whenever it has been updated/saved. I know it shows this message when you save and I think it is shown in multiplayer when people join/leave. So my guess is that you did something to update the playernamehere.c4p.