Deleted item still appearing in Advanced Filtering Panel

Hi everyone

My CRM contains an option set list of Titles (Mr, Mrs etc) from which I recently deleted (not deactivated) the Prof Sir title.

When I try to search for all records with a Title of Prof Sir using Advanced Find, the title is not there (as it shouldn't be!). Please see image below:




However, when I use the Advanced Filtering Panel functionality, I can still see the Prof Sir title as per the image below:



Does anyone know if this is a bug within Dynamics, or whether I need to remove the title from somewhere else too?

Many thanks
Jon