A salient point here being glossed over is that in no way is it normal or acceptable for other players to steal expended Tornado grenades.
1) You should not expect that to happen and normal and organized game where honor is a tenet.
2) If it does happen you should call out full stop and find out who's pocketed them.
3) If no one owns up post up the event details and player names. The hate machine will do it's job.
4) Regardless of other details it is prudent to police up gear like dropped magazines, grenades and weapons as soon as possible and not at the end of the day or game.
Airsoft, where nothing is hurt but feelings.