My wife found a plastic basket had been chewed on. The small chewed pieces of plastic were inside the basket. Nothing else in that cupboard was chewed though. We don't know how long it's been like that either. No signs of mouse droppings.
At the last house we lived in, we had two mice over the years that we were there. We caught them both. Unfortunately, one of them died in the trap. We use live traps, but I had baited the trap for weeks, and checked it daily with no sign. I forgot about it for a few days and when I went back, it had a dead mouse in it.
The first one we caught about a year before was still alive. It was a much larger trap too. Click on the picture to see the little trapped critter.
I baited the trap with peanut butter and left it in the cupboard where the plastic basket was. These little critters amaze me how they manage to climb up into the cupboards, and navigate from one to another without any obvious access.
If there is in fact a mouse in the house, I hope we catch it soon.