If there is sludge in the pan, it seems to me that the flush worked. The problem would be in order for that much sludge to form in only 73k miles all the preventative maintenance prior to that was severly neglected. The flush caused the sludge to break up and clog the lines leading to the engine being starved for oil.
The maintenance records for the first 73k miles would also be important. How often did you change the oil? What brand and viscosity of oil did you use? Was the engine mechanically sound to begin with? (UOA could establish mechanical stability) What were the conditions that led you to believe a flush was warranted?
There is so much more information necessary before culpability can be established. You have to examine cause and effect all the way back. Simply having the engine flushed didn't cause the engine to fail.