Add Thread Prefix to existing Thread?


Well-known member
I have prefixes set to default on my Categories so all their threads inherit their Category prefix
I moved a few forums to a different Category and now their threads dont display the new prefix. But it's right there if I manually edit by thread tools and no other prefix is there to select. So the thread knows which one is correct but is not displaying it without an edit.
What do I do to fix this please? Omigod not a query please not a query I'm not clever.