Given that the amount the person was bidding on was larger than...

Given that the amount the person was bidding on was larger than the disclosed short position, I reckon it was a back/front office screw up. The following is just what I reckon is a plausible scenario, not anything I can prove.

Let's assume that an insto had held on to his long position all through the offer to retain optionality. When the offer goes final, unbeknownst to the insto the custodian of the stock accepted the offer. The insto sees the stock trading at a small premium and sells the stock on market - only to find out the stock had already been pledged into the acceptance facility. To his horror, the insto finds himself naked short a long line of UGL whilst CIM have already swept up >95% of the register - he has no way to cover. Compliance, mindful that "he who sells what isn't his'n must buy it back or go to pris'n" take over management of the position and desperately try to buy it back on market. This causes the mental short squeeze we've seen over the last couple of days.

Outcome? Insto loses his bonus, custodian gets fired, some lucky punters get a 70c premium to the offer. Happy Christmas.