Q: I am having a problem with a student not appearing on a search. He shows up when I export my class roster, so I know he has an account. I can see him included on a roster, but cannot manage the account.
A: It appears that your student never confirmed his account, so he is still what we call a "stub account" (invited user).
He shows up on the Roster list in anticipation of him confirming his account, and even in the gradebook so that you can start inputting grades for him if you need to. However he technically does not have an account until he confirms his invite.
You can recognize users who are still stubs by the greyed out user icon to the left of the account name, the "(unconfirmed)" on the right side of the account and because they still have an invitation code listed.
Once your student confirms his account his username should start showing up on all searches.