My first tree frog was a Gray Tree Frog rescue many years ago when I was around 12 or 13. She had a defect where the toes on her back leg were all morphed together. She lived for about 5 years in captivity before she passed. One of the best frogs I've ever had! And I also now have a FBT that only has 3 feet. One of his legs is just a stump. They are very hardy and adapt to these injuries very well (after it has healed and gotten away from infection at least). I doubt he/she will grow them back, though I am no expert on that subject, however, I'm sure he/she will live a long happy life with his/her handicap. I hope for the bests or both of you!