Options for filtering on a Member Field Name if they are no longer part of the Org?

We have a member who has left the company therefore his user was removed from the Organization. There are still some incomplete items in our Tasks app with that user as the member assigned. We are unable to filter for them however (which makes sense as they aren’t a current option in the org…)

In Podio there used to be a hack where you could save a view that was grouped by Member. Then seeing their name and clicking that added that member in the filter which could then be utilized. This hack doesn’t seem usable in Tape.

Ay tips on how to accomplish this so we can easily reassign their outstanding tasks to a current user?