Hi! Sorry I was away for the weekend. My work days are long.
You've gotten some good advice. Continue to feed away from the rocks. A luke warm dechlorinated water soak with about 3 good drops of honey in it helps them to pass their feces. No need to heat the water beyond slightly warm. It is likely he spit out the rock or you saw a cricket. Hard to say. American bullfrogs often spit out any prey that they attack and decide they don't want. Mine has actually taken in a dubia roach, spit it part way out, turned it with his tongue in a different direction and then takes it back in. Pretty slick. They can, however, be aggressive eaters and taken food in fast, before they realize what they've grabbed. There is always risk of impaction anytime any rock is accidentally eaten. Monitor carefully. He would have a hard lump on the left side of his belly after eaten and on the right as it moves down the intestines. Mineral oil can be used, but with caution. It is safer to use honey soaks. It sounds as though he is fine. If he continues to act normal, eat, and poop without difficulty, he should be okay.
Oh, a good tip for soaking is to place him in a small cricket keeper for the soak and put the cricket keeper right into his tank, if there's enough room. Then just pick him up and over the edge of the keeper. That way, if he's being crazy he won't jump or fall far. Then just remove the keeper. It's also a smidge less stressful that way.
Keep us posted! I hope he is okay.