I would have to agree.
Add a new Field to your client side:
(http://osticket.com/forums/showthread.php?p=4773&posted=1#post4773)
If you are trying to make it easier for the client to log in by only having to remember 1 number, inform them that they can use the number of a closed ticket as well. Or copy and change the Auth function to look for an email address and the customer number. This way all of their complaints will still have a unique ticket ID.