When we moved into our current rental house, I noticed mouse droppings in the kitchen drawers closest to the sink. I found a small hole in the back of the sink compartment, and a crack in the outside wall behind it. I filled up the wall crack with caulk, then filled the hole with drywall plaster.
Apparently there were still some mice who were hiding in other places and were now trapped on this side of the escape route. Our cat found them before we did. Finding and fixing a possible mouse hole is good, but it's no guarantee that all of the mice are on the other side of that hole.