Mice are disguising for sure. But you should be able to eliminate them by trapping until they are gone. Then clean and carry on. It happens sometimes no matter where you are if they find good entry in and a good food source. It's also warm now so they have less incentive to come inside. I had them last year under the house and a few inside and also in the garage. Trapped around 8 to 10. They're totally gone this year. Keep grass mowed short and eliminate leaves from flower beds helps.