Nautilus Dolphin part

One of my family members ran our Nautilus Dolphin with the filter removed. It obviously sucked up a bunch of stuff and it all got wrapped around the impeller. I removed the cover and cleaned everything out. There appaeared to be a rubber piece between the impeller and the cover. It didn’t survive. I can’t find the replacement part anywhere.

http://www.inyopools.com/parts_maytronics_dolphin_nautilus.aspx

I assume it was a part that was supposed to be there. Maybe it was a random piece of debris that happened to get stuck there. I can’t figure out where it was supposed to be attached. Any ideas?