I performed a 'Change as Technician' on a requester in my system and the user can no longer be found in the Configuration Wizard - Requester List, the Configuration Wizard - Technician List or any of the 'Technician' dropdowns in the system.  The "invisible user" is still able to log in to the system and is presented a Technician UI.  I can no longer manager the user as a technician, i.e. add the tech to support group, etc.

I can find the technican with the following query: 

select hw.technicianid"Technicianid",a.first_name"Technician",sd.status"Status" from helpdeskcrew hw left join sduser sd on sd.userid=hw.technicianid left join aaauser a on a.user_id=sd.userid

I can no longer manager the user as a technician, i.e. add the tech to support group, etc.