Did you have any purposes in mind? An A record for the apex of the domain would be easy to find with dig or any other DNS client. I agree with the hypothetical

Did you have any purposes in mind? An A record for the apex of the domain would be easy to find with dig or any other DNS client. I agree with the hypothetical though, your DNS provider can set records that you didn't request, could hide them in the console, and detecting these would be hard in the general case.