Hm even if a native to the area the temp in that tank could well exceed the temp/ humidity outside if it was 75 out but your in a glass jar your gonna get hot fast. For a small frog this could have been to much. Any way there was another frog in the tank? You should clean that entire tank just in case. You don't want two frogs to be lost also you may want to think about getting some gauges. The water did you treat it? I'm sorry about your frog and good luck with the other little frog.