Why did Vince leave his gun on the counter at Butchs apartment when he went to the bathroom?
Quite simply, he didn’t, the gun belonged to Marsellus. Vince was clearly with somebody else at the apartment as he didn’t react when Butch came in, thinking it was his partner. Jules had given up ‘the life’ by this point and Marsellus was probably filling in on this job. For further evidence look at the scene where Butch runs Marsellus over; the ‘big man’ is carrying two cups and as he is near to Butch’s apartment, we can assume that he is Vince’s partner.
