Next time you take it for VEIP they'll put your cap on their tester, note that it fails, but maybe not say anything, because it doesn't keep you from passing the emissions overall.

"MVA VEIP - Gas Cap Leak Check. In addition to the emissions test all vehicles also receive an advisory gas cap leak test.
The cap is placed on a testing adapter and gently pressurized with air to ensure that it seals tightly. While the results of this part of the test currently will not cause your vehicle to fail the emissions test, a gas cap that fails should be replaced in order to reduce gasoline vapor loss. Gasoline vapor loss contributes to our current pollution problem, and can also decrease your fuel efficiency."
--
Art Benstein near Baltimore

"You can say any foolish thing to a dog, and the dog will give you a look that says, ''My God, you're right! I never would've thought of that!'" (Dave Barry)