If you have seen one mouse, there are many more. It may have been a "field mouse", but it's moved up to "house mouse" now. I avoid poisons because of the dogs, but mice and rats carry diseases that can make you and your pets very ill. Leptospirosis is particularly nasty and is often misdiagnosed in pets and humans, resulting in hearing loss, extreme fatigue, vomiting, fever, diarrhea, skin rashes, and liver failure.
Wrap your food up tight, take out the trash every day, keep the fire wood away from the house, don't feed the pets "at will" or outside, buy some traps and get it over with.