This has happened to me a few times….
A user leaves and his or her AD account is deleted.
Sharepoint catches wind and marks the mysite as abandoned and emails the manager it had in User profile service, then deletes the User profile.
Then a day later someone emails the SharePoint Admin (me) and says they aren’t actually that person’s manager.
The link in the email to the mysite doesn’t work and it’s easy to think that it just auto deleted.
Checking the site with powershell (get-spsite http://mysiteurl/person/userid) shows the site collection still exists.
I found the answer at Demand Prasad’s blog.
To see the contents of the mysite, you need to be one of the two site collection admins as assigned in Central admin, but you can’t use central admin, you have to use
stsadm -o siteowner -url http://mystite/person/userid -secondarylogin domain\userid
The orignal blog post does a great job of explaining it so head over and have a read.