Keep a very close eye on him.
The stress during the adjustment to a new enclosure predisposes them to opportunistic illnesses
when their 'resistance' is down.
Have a herp vet on-hand!
Cover three sides of this tank and keep things as quite as possible.

Sometimes during color changes there are spots that appear temporarily

Post a photo if possible , please

"sleep under the moss in his tank"
1) a whites sleeping under the moss is likely an indication the humidity is too low despite this species can tolerate variables
**** be sure he has a clean, shallow water dish ( to soak) ( water to his chin ) filled w de-chlorinated water ( change it daily when he is asleep ... so he is not disturbed )
2) ???moss??? what moss ??? If you have sphagnum moss in the frog's enclosure ( as many big box pet chains do ) remove it asap as it can cause intestinal blockage if ingested accidently

3) be sure he is warm enough !

Plain white paper towel can be used for substrate / dampened w de-chlorinated water temporarily or permanently