Congratulations on your new purchase. I hope you don't keep your new little froggy with any fish b/c that kind of aquatic frog will eat em all up once it gets to a certain age.
To answer your question, I have had a frog in my tank lose it's arm mysteriously. I was very worried for him, but could not figure out how it happened (he wasn't a clawed frog, but aquatic, so same difference). Anyways, he recovered, regenerated a tiny little nub and lived for a couple years after that, and one day I tragically discovered the reason for the arm loss. Apparently, he climbed up to the little slots in the filter and stuck his leg in there and couldn't get it out b/c I'm sure he was fanning out his toes. Well, he drowned, as he was an airbreathing frog and it broke my heart...I called him "nubs". I figure, his arm had a similar fate...however he was able to rip it off in time. My advice try to get some thin netting to put around your filter uptake...take it off regularly to clean it. Haven't had anymore froggy fatalities since. Good luck and enjoy your unique new pet!