Requester drop down - Cache?

Discussion created by 7921052 on Jan 8, 2016
Latest reply on Jan 13, 2016 by Yuval Pecht
Where is the requester drop down list pulled from? My presumption would be that it pulls directly from the Users list, however, there is an email address from a removed user that continues to appear. Is it perhaps "cached" somewhere in the "cloud"?

The cached email is highlighted:

That email belonged to a user account that was deleted.