Hello

the only way I can imagine is that it was a registered user who was deleted in the meantime. Are there other admins apart from you?

It seems that davwat did exactly that. But there (for me) are some additional question. Is an user able to delete his own account*? Would that be desirable**?

* Sorry that I didn't test it myself.
** I think it is not.

Tschö, Auge