The very first question is are you even required to register at all.License and Registration, please.
The better question is are you required to show your drone registration. The answer is yes.
In the very near, but TPD future, you will also be required to show your pilot's license. The requirement exists today, but the FAA has yet to create the test. Once the test has been implemented, one will have to carry and show proof of passing the test (AKA, a pilot's license). The test is required regardless of the weight of the drone.
Nick
If not, and you are flying the Mini as a hobbyist, you can tell them you are exempt. No requirement to show anything. They only have jurisdiction to ask for proof from nonexempt drone pilots.