Even when I’ve worked with Realtors, they haven’t had access to permit information. They have went back to the seller or seller’s realtor to inquire and ask for copies of the permits. Maybe I’ve had lazy Realtors, I don’t know, but that’s what they have done.

I’ve generally found that sellers that have done the proper thing and permitted all changes have kept a record of it and are more than happy to show you. To my way of thinking, failure to produce the proof (“my dog ate my permit”, “of course I did, and I don’t have to show YOU”) is a pretty sure way to determine that no, the permit was not filed.