I had something similar happen to me earlier. I found Fluros or whatever that coeurl NM in temple of uggy is called and when I went to claim it over this JP paladin my controls went on the fritz and instead of locking on I rested in front of a bunch of tonberry. In a futile effort I used hundred fists hoping to kill it before I got massacred by tonberries unfortunately blaster got the best of me and I died with it at 3%. Meanwhile the JP paladin just stood there and watched me die to take it at 3%.
Alas, my mistake, my error, my death, and therefore my loss of claim for him to take full rewards from. At least he gave me a raise, but needless to say I was pretty pissed. Mainly at the fact my controls went haywire somehow ><