Could be a network connection issue. Also, if very low on time, a move might not reach the server before time expires, even though the move will appear on the board.
Confused

Check your game again, probably the move Will not appear, meaning that due to connnection problems your move was made after the time ran out.

I just lost a game on time, but i did the last moove.
How ?
Just, how ?
Is there something i don't get or is it some sort of software issue...?