BIG UPDATE All of the 426 Mews are finally together and even the mysteries about their placements are solved thanks to @Sabresite's newest findings. A completely new Set of 5 Mews was discovered with the initial seed 0x5E2B. In fact it appears Mew #1, #2, #4 and #5 of the Seed 0x6065 (which I reconstructed earlier and we believed them to be in the Party) were deleted in order to generate the new Set. This leaves number #3 of Seed 0x6065 (to be found in Box 1, Slot 1) the only Mew of its Set