My MP01 was missing one ladder panel but Takara sent me a pair of them, most likely because they manufacture left-right parts like this in sets. This means that if they do decide you send you replacements then they should send you both. There's no point in HasTak keeping the other one... for example, if they sent you a left headlight panel what on Earth are they going to do with the right panel? It was probably for this reason that I was sent both ladder panels and I'd imagine that they'd do the same for you.

Anyway, good luck!