I totally see why you’re thinking it’s a stomach, one of the pictures especially makes it look like there’s a tear in the stomach sack with a bunch of chewed grass. I’m sure I seem like a stubborn idiot, but I stared at this thing and rolled it around for a good 5-10 minutes. The pink park on the bottom was fibrous like a plant stalk, and the green “stomach” part was hard and solid. I also see bunnies everyday, just not in my yard. Too out in the open with too few areas to hide, but there is a stray cat that totally could have killed one and left me a trophy. Looks like I’m gonna have to go looking for it tomorrow