I'm running a campaign and last time we thought one of the pc's died. He didn't have much health anymore en when he got a full on hit, he died instantly. It was late so we stopped shortly after that.
A short time later, out of game, the pc realizes he forgot to include his extra hp, they just went up a level and when he rolled for his new hp he didn't write it down. If he had included it he wouldn't have died, he would have had enough.
So what would you guys do in this situation? Just say it's your mistake and you're still dead? Or give him his extra hp and let him live because he really does own that hp?
Edit: Thanks for the advice! I guess I'll let it slide this time and let him live, story wise it's no problem.