The short game ( all of it, including shorting, covering, and MM action ) only took up 22% of today's trading.
So it seems that shorts were not a big influence today in keeping PPS down. You could always consider naked shorting though, which does not show up in the daily stats, as a possibility. Looking at the accumulation/distribution chart for today I see early buying followed by a slow, fairly steady sell off for the rest of the day.
This might explain the whole twice normal volume and no big increase in price thingy ;)