Yes, this site is the official game (for itch.io), and I do not understand these things well, because I download here and to this day I did not make purchases in the game, but you could try for Steam, I see the purchase of the map be held most of the time over there
Hmm, maybe you could send them an email. Sorry, but that was all I knew, because I play on mobile devices and have not yet made in-game purchases. You may be more lucky to email them if they don't answer you here
