Finally got around to looking at this. The way grenades are currently implemented, they fire a bunch of projectiles in random directions. It's entirely possible, though unlikely, that the projectiles will all fire in a direction away from a player. Also, grenades are handled server side, so there's not really a way to hack them (unless the server itself is running some sort of hack). I think this is just a case of luck.
The only thing that looked odd was the second grenade after you died. I guess your teammate threw that?