Not end of game scenario but I often get the call "head injury sir, head injury sir" and if I'm unsure or haven't seen any obvious incident I have to stop the game to cover my *rse.
Often it is just a tired or old or unfit player who is just a bit shook up or knackerd and opposition are usually attacking.
In these scenarios I insist he goes of for a local HIA as a minimum.
Don't take the p*ss lads!
Had this in a mismatch fitness wise the other week, was 18 - 0 with 15 to go, ended 60-0, losing team were frustrated and had shipped a few in quick succession, then they got turned over in opposition 22, 2 quick passes and winger is off to the other end and another try. As I walk back for the conversion I have two or 3 players screaming at me that there was a head injury, why didn't I stop, try can't stand etc, etc (I've seen and heard nothing so no reason to stop) - I suspect at the time it's a manifestation of their frustration, and advisor post match agrees I was right, you can't stop a game just because someone plays the head injury card - of course if you see something, that's different.
I got the opportunity to watch the incident back, turns out the head injury was one of his team mates coming in to guard and create a ruck, he went off feet and poked his team mate in the eye with his hand trying to support his weight!