The short seller will incur a loss if the price of the assets rises (as it will have to buy them at a higher price than it sold them), and there is no theoretical limit to the loss that can be incurred by a short seller:)
At best a short at 6.20 could have traded for a 60 cent profit today on perhaps a couple thousand shares.
But if he missed the bottom and held on he has a loss.
The run in the last 45 minutes was extraordinary. For 45 minutes 95% of ticks were up or sideways eating through all the shares on the offer. There was one very short dip lasting about 3 minutes. About 140K shares traded - up up up.
It seems to me that there were buyers sitting out there ready to buy lots of shares at this one dropped and they decided to buy out the offers at the end of the day.
I bought shares near 6 before it broke to 5.60 and glad I did.