I keep an old college ID card around for that purpose. It is issued by a state agency, the college isn't going anywhere, it has a unique ID number that isn't used for anything else, and I can use it get into the credit system becuase I have a way into my loans through thier financial aid office. And I'll be remembered long enough that if they ask around, they'll find someine in ten minutes who can describe me and confirm the picture on the card is me. And the alumni office has my perminant address on file.

And it still works to let me into computer labs. Until they revamp the system entirely, it still will, so if I can get there, I've got shelter and communications.