Yes, it seems an odd conclusion. Presuming that the pants in question were fairly tight fitting, which seems likely for a young woman out bar hopping, and noting that they were wet, we can conclude that the pants were probably sticking to the wearer. The natural way to remove them would be to start at the waist band and roll them off rather than sliding them off, so that they ended up inside out; this would be the case whether it was the wearer or someone else who was removing them.