Keep track of which players have already found their objects.

* All players keep track of which players have already found their objects, even when they are missing.
* When players rejoin the game after losing their connection, they locally re-trigger the handlers for all players who have already found their object. (Question: is this necessary?)
* Players publish whether they have found their object along with each position updates. This ensures that spectators do not need to keep track of any state and can connect and disconnect at any time.