Cannot remove deleted user from people picker - SharePoint Foundation 2010

So I think I've read all the people picker articles here and I can't find a solution so I thought I'd start a new thread. Here is the issue:

A user was deleted from Active Directory and removed from SharePoint Foundation 2010. The user was still showing in the People Picker within the site collection, so we have performed a few things to try and get rid of this user.

User is deleted from AD
User is deleted from SharePoint Site Collection
Have tried stsadm -o deleteuser
Have removed all mention of this user from UserInfo table
User does NOT show in https://<SiteCollectionURL/_layouts/people.aspx?MembershipGroupId=0
Cannot find any mention of this user anywhere.
Ran a full crawl as we read on a forum somewhere that it might help.
If I try and add the user back to SharePoint I get "The user does not exist or is not unique"
If I try "stsadm -o deleteuser -userlogin DOMAIN\USER -url https://<sitecollectionurl>" I get "The user does not exist or is not unique"

I am not sure what else I can try now. Can anyone help?

Thanks,

Vinny

Vinny