I was participating in a FIDE-rated rapid tournament a while back (15+0, if it matters for the rules), and had finished my match, and was watching another board. White had about 10 seconds remaining on the clock when black moved a pawn which put the board into position of a stalemate (blocking the forward progress of white's only free-to-move pawn). The white player failed to realize in the 10 seconds that they didn't have a move (there were still a few pieces on the board, some pinned, others just blocked, so it wasn't immediately apparent).
I saw the position was a stalemate right away, but neither player recognized it, and since white's time ran out, black took the victory and reported it. In this scenario, should I have:
- Notified the arbiter of the discrepancy
- Accept the fact that white effectively surrendered by shaking hands and accepted the defeat
- Notify the players directly (before anything is reported) and let them resolve it themselves?
As well, would the stalemate stand even if the timeout was hit, or must the players acknowledge a stalemate for it to count (regardless of white's inability to move).