Maybe the other rogue had a bit more than them? Maybe they didn't bid because they were waiting for void? Maybe the rogue was friends with the other and was going to let the other one have it? Maybe he did bid the same as the other rogue and lost the roll for the item as if you bid the same amount a roll determines winner.
What other 5k dkp rogue? Why didn't that 5k rogue win the Imp Helm the first time?
That seems likes a pointless question