You don't have a water bowl in your tank? I would strongly advise adding one. In the wild there are obviously no bowls exactly, but they have other options for getting water (dew and rainwater collects in leaves and crevices in branches even high up in the trees, or they can come down to the ponds or puddles). Especially if you are letting your tank "dry out" sometimes, they need a source of water available while the humidity is low (although you should also try to keep humidity relatively stable if possible).
in captivity our frogs depend on us for everything, so it is important to provide them with conditions as close to ideal as we can. In the wild, frogs can move to another location if they don't have the right humidity/temp/water, but in a 10 gallon tank they can't just find somewhere else with different resources.