I find mice in about 3-4 hives come spring. These were likely dead outs as Allen mentioned. On more than a few occasions I have found dead rats near my hives, very close to the hives in fact. I believe they were trying to rob some goodness and the bees wore them out! One such time I had a really aggravated colony and a freshly killed rat right in front of the hive.
Ed, as long as the equipment is still usable the bees won't mind that a mouse had been in there.
...JP