Mouse entry

Hello!! I’m curious, we had a dead mouse in our laundry sink in the basement. I have never seen mouse droppings in our house other than behind the stove when we first moved in, 2 years ago, which has not made a re-appearance. I always keep an eye out for droppings since I am totally petrified of mice. We purchased a UV light to check for urine, and did not see any. Mind you, this was a 7$ UV flash light from home depot. Probably not the best, but still nothing. Our laundry sink drains into our sum-pump with the drain about half a foot from the ground or where the top of the water sits. maybe a little less. we have a basement window above the laundry sink and to the side which is basically completely sealed. I say basically, because it’s an old window and it wouldn’t surprise me if there was a tiny crack hardly visible. We keep a fitted piece of wood over the window well. any idea how this mouse came in? i’m assuming it was a baby since it was TINY. any suggestions or anything else i could look for? thank you. Brantford.

Mouse entry: Mice can get in through cracks as little as ¼” (about 5 mm). Also, do you have any cats? We live in the country, and occasionally, one our cats will bring a ‘present’ into the house.