Dang. Don’t pick those up I guess.
I don’t know how much explosive is in one of those grenades, But I reload my own cartridges and it is amazing the amount of power that is contained in even a minute amount of smokeless powder. Some of the pistol cartridges that I reload which are powerful enough to kill a horse, take only a couple of grains of powder, which is 4.6 thousandths of an ounce. It is also amazing how fragile our bodies actually are. So I doubt that the grenade was anything out of the ordinary.
Do not pick up Flash Bangs.