So, Mateons and Plateons had such a strange piece of blueprint, huh...
This makes me wonder. Mecateons are higher in hierarchy, and they sure wouldn't let their foot soldiers hold onto something important like that, unless they were already preoccupied with something else.

(Mecateons and MT-09 are deeper in the Boswell Fields. If they really have a fragment of the blueprint, I should be able to retrieve it by defeating enough of their troops!)

Are you sure...?

We can't exclude the fact that Mecateons could already have another piece in their hands. Or even worse, that they passed it to their MT-09 units for deeper analysis...!
You might want to travel deeper in the Boswell Fields, and hunt Mecateons and MT-09 to verify that hypothesis.