[otrs] locked ticket to System OTRS

Hello all, just joined the group and hope you can help me out. I am admin for our OTRS but seem unable to do anything with a ticket that a user accidentally changed owner to blank. Due to her changing owner to blank, it is now assigned to "n/a (System OTRS)". I can't move it to spam, close it, do anything to it. Always says im not owner and so cant take this action. She can also not touch it, same error about not being owner. I assume you can't login as system otrs user so unsure what to do. all i want is to either close or remove this ticket. any help much appreciated. Neil