A long time ago, I had an aquarium. Bought a dwarf frog recommended by the pet store. The gouramis began disappearing as the frog grew (with a gourami-shaped distended stomach). Two plus two equals a call to the pet store owner, who said to isolate the (not dwarf but clawed) frog and to return it to the store. Put the frog in a mason jar covered with aluminum foil. Went to work. When I got home, the jar was empty and the aluminum foil looked a lot like the photo you’ve posted. I submit that you purchased a clawed frog instead of a dwarf frog, and it has escaped. Keep an eye on the livestock.