As far as I know, nope. It keeps the magnet from rubbing against the inside of the wetside housing. It is entirely possible (assuming it was there when you started) that it rubbed off. Any thin nylon washer should do though as a replacement.
First see how easy it is to spin the magnet. One problem with these pumps is that if the impellers sticks it'll torque the wetside right off the glass.
Check that there's that clear nylon washer between the magnet and the plastic of the wetside so they don't rub. Double check that your spacers are properly done to your glass thickness so the magnet can actually grab onto the electric motor's magnet.
I have not cleaned either of mine in over a year.
If I do clean them I first chuck them in a bucket of 25% bleach for a while rinse and then in a mild muriatic acid bath rinse and stick it back on the glass.
Vortechs come with a little plastic mounting piece that has double stick tape on it - Provides much needed support to the dry side. Are you using that? Seems like the spacer may need to be adjusted as well. May have to go with what works and not the spacer markings.
My rare Vortech-cleaning event is simple with the wetside getting an afternoon bath in vinegar and briefly scrubbed with a toothbrush. Yes, I've used the wrong toothbrush before...