and he says the 'reset password' option doesn't work because he didn't give an email address when he signed up (is that even possible?)
Yes. Those are guest accounts. If you log out and don't have it attached to something you'll be unable to get back in without contacting support.
Is there any way he can get in touch with Inno support and recover his city?
Yes. They'll need to go to the
Support Page and click "Contact Us" (it'll be a yellow button)
If they're not logged in then they'll need to choose which server to contact. In this case English (Int)
They then should see this page:
Clicking on the link for not remembering username or password will allow them to communicate through email. We'll then provide them with a list of security questions. They'll need to remember various aspects of their city to confirm who we're talking to and that we've located the correct account.
Once we've confirmed everything they'll need to provide us with an email to attach to the account for them to use the reset password option
