Each rv is different even same models as the assembly line has different people doing things differently. Look at the side of your frame. See holes where hydraulic rams operate the slides if that model has hydraulic slides? Mice can enter there. Have 6 point level up? The front landing rams and the mid leveler rams probably have entry areas for mice. Crawl under the rig and look for gaps in the coroplast. Mice can enter there. Nothing beats an owner that does a detailed check of their own rig.
2012 F350 6.7 L dually, 2013 3800RE with 6 pt leveling, Sumitomo 17.5" load range h tires, Samsung 18 cu ft residential fridge, 8k Morryde I.S. with disc brakes. Full timing since 2012.