my experience is that frogs tend to stay at the edge of ponds etc and not to the center, they also when distrubed head to the bottom as fast as they can to get in the mud. I suspect that the reason trout arn't found with more frogs in their guts is that frogs make it very difficult for the trout.

I see no reason why if given a chance a trout wouldnt eat a frog, any more than a trout wouldnt eat a mouse if given the oppertunity.

Eric