Short sales on GRNO are miniscule except for the jumps on the promotions http://www.otcmarkets.com/stock/GRNO/short-sales. You're looking at instantaneous settlement fails which are cleared quickly. If there were significant short positions even open for 3 days, you'd see GRNO on the Reg Sho Threshold security list.
There's always going to be some demand. The low trading volume indicates it's not much and the lack of many trades at the ask (at least with a modest spread) indicates to me it's not serious.