I have two theroys to wat happened...I think i saw wat it was..its really hard to be certain but it seems as though the grenade deflected the shot..it was the only thing that was in that area at the time...and it was ur enemies grenade as well...look at it again..like u said it didnt hit the wall..nor ur opponent for sure...so it had to be another object...or it was a glitch
Bullet trails are done client side - on the host`s XBox, you were in front of your teammate when he fired, so the game says you got hit in the head. The bullet trail is then calculated after you receive the data stating you`ve been hit in the head with the current data of where you are (on your XBox) and where your teammate is (on his XBox.) This is why you get bullets ``going through walls`` a lot in Halo 3. Basically, other players` bullet trails mean nothing, they are an aesthetic touch done client side. Sorry if I haven`t explained this well, but I`m tired.
I`ve done that before kill the team mate standing beside be I checked and the bullet never even touched him it went straight and hit a wall and stopped