I would say this is possible but not likely. If so it would be in the # kills before 3 of us died since 2 of us watched the scoreboard after our death.
FTR I'm not tying to just dismiss everything all of you say, just trying to scratch things off the list that we had already considered. I value and appreciate all of your help since I'm still learning a lot about the game...
Another possibility?
One of the players in the group had us try this thing where we would kill the last zombie by the teleport then quickly teleport as the rounds were changing so that when we got back to moon the new round was just a partial round. Not sure if this is considered a "glitch" but if it is could this possibly have caused what happened?
I did the round shortening glitch on moon with 2 friends, and we ran across a round 36 that didnt end. When we died we had each killed over 2000 zombies. I have never seen a round 36 - 3 player game with 6000 zombies.