You won't hear this everyday, but earlier this month, referee Mike Beltran had actually disqualified a fighter for not fighting. It was at RFA 15, where Daniel Aguilar (10-4) had one too many butt-scoots that got him a rarely seen disqualification loss for refusing to engage against his opponent Sam Toomer (8-0).
Aguilar, who had all 10 of his wins come by submission, didn't want to stand with his opponent and repeatedly flopped on the ground, begging Toomer to enter his guard. As he refused to engage even after multiple warnings and a point deduction, and this prompted the experienced (and epic-ly stache'd) referee to make the call after repeated 'fouls'.
Here's how Sherdog is calling the victory:
Technically though, it's a DQ loss because of 'Timidity', which is listed as one of the fouls in the Unified Rules of MMA:
23. Timidity (avoiding contact, or consistently dropping the mouthpiece, or faking an injury)
Timidity is defined as any fighter who purposely avoids contact with his opponent, or runs away from the action of the fight. Timidity can also be called by the referee for any attempt by a fighter to receive time by falsely claiming a foul, injury, or purposely dropping or spitting out their mouthpiece or other action designed to stall the fight
Watch footage of the said fight above, which includes statements made by Beltran as he spoke to Inside MMA about making the decision to stop the fight.