Especially if you were looking during mid-day, when they are active, those caterpillars will curl up and literally JUMP off the leaf to avoid detection -- remember, they think you're a bird coming to have them for lunch! If you found
3, there are probably at least 3 more.
If you have rabbits around -- ooooh! those pesky wabbits! They've chewed several seedling shrubs and trees I put in nearly to the ground! I'm in the process of caging and/or fencing
They've got plenty of dandelions and clover