I haven't heard of cardboard to protect against caterpillars before! Amazing :P We get them but they tend to eat things that overgrow. And get eaten by the chickens. Yummy :P
@ Join the Masquerade That's exactly it, which was why I had a feeling nothing would happen. So next time we will be getting seed potatoes and doing it the right way. And yes the tomato survived, though it was being eaten by caterpillars! Hence, the cardboard pieces, which work really well surprisingly.
Might not have been your fault. Some potatoes from the store have been treated so that they won't sprout, as they're meant for eating (I'm assuming that's where you got them from XD) And YAY the tomato plant survived!