Yes, Waste is referring to forcing water from the pump inlet back to the skimmer in a reverse direction to try and force any obstruction out the pipe the way it came in. An obstruction would have had to have gotten past the skimmer basket though. Maybe they ran without that? Also, how did they manage to burn up the motor and what kind of pressure are you seeing at the filter inlet? That's what the pressure gauge measures, filter inlet pressure. Can be valuable clues as to what happened. If they somehow managed to run the pump with the return blocked, water in the pump but no flow, they may have heated the water to near boiling in which case regular PVC will soften considerably and air leaks could develope at the pump inlet fitting.
Al