I'm currently on honeymoon in Toronto from the UK but could not find a copy of this for Vita anywhere today. Undershipped or just more popular than expected?
I guess both. Atlus tends to do a small first shipment for all of their games to keep overhead costs low. I don't support the practice of pre-ordering in general, but always preorder Atlus games.
But from what I hear, this game is selling quite well also.