A patron's ComCat account is created the first time they log in. If a patron has never logged into ComCat, the system does not have that patron's information.
In order for a staff member to request items on behalf of a patron, that patron has to have logged into ComCat at least once.
If you are requesting an item on behalf of a patron and do not see their name in the patron search results, it means they do not have a ComCat account. Have the patron log in and then try again to place the request on their behalf.