Maybe a dumb question--While sanding a small piece, the entire sanding pad flew off and went across the shop. Not just the sanding disc--the entire plastic/rubber pad. The sander is an older Quicksand 333 model with 5 holes with hook and loop. I was putting some downward pressure on it at the time. I know there are replacement parts--Any idea why the entire piece came off at speed? All 3 mounting screws remain in place on the sander. Can I fix this by simply installing a PC part #85 (from the parts diagram?-which is replacement part 13904). Thanks, Larry