I've had a lot of bluegill that have went after my frogs when I've used a smaller frog like the lunkerhunt pocket frog. I've actually caught several of the larger bluegill on it, one being the largest bluegill I've ever seen, over a pound on my calibrated estimation, he had a solid 1 1/2" wide mouth! I caught him right at the end of the cast, I was standing on a culvert that is an ambush point.
A lot of times, when its a bluegill, they will grab it and swim, even fight a few seconds, but when I set the hook it doesn't set because the fish only had the legs is my guess.
My thought is, you probably have missed some bass, but also have had bluegill going after your frog and those are much harder to get because of their smaller sized mouths.
I love fishing frogs.