I am pretty sureThat all short positions are actual shares borrowed from a holder, like a bank, with a pool of free shares that noone owns.
those shares are simply tossed around, and when the record date clicks its snap shot, those real shares wether short or not just spawn the rights. So the shorts were never down rights, they were only down actual shares, which they did sell to you as normal shares and then the snapshot created the rights.. so the shorts do not owe rights, just actual shares that were already sold.