I have a calendar event that includes a contest for registered members who rsvp. I have one guest (unknown) RSVP from before I noticed that the guest group had RSVP permission. Is there a safe way to remove that guest RSVP?

Edit that Calendar and remove permission from guests. But I don't think guests can RSVP. Probably this is a removed member and as the system isn't finding tge ID, display Guest.

I removed the permissions but the count (and default icon) remains.   It's not a big problem in that I can easily work around it, but my sense of tidiness makes me want to clean up the evidence of my error