There is more than one species of caterpillar that can do this. They're hard to see, so their presence usually isn't noticed until they've done considerable damage. The leaves which have already been munched on will not, unfortunately, regenerate. Once control is achieved, though, no other leaves will be damaged.
Orthene will certainly work, but you really don't need such a heavy duty chemical. The soap may have helped, but soap based insecticides designed specifically for plants would be a surer thing. I've found neem extract in oil to be very effective - kills the caterpillars and the oil smothers any eggs. There are several brands available of this safe product.