someone went on the purchase website and, putting my email address in the "purchase as gift" option, bought among us as a gift (I'm on Windows) and there aren't any among us files or any emails even mentioning a gift. i didnt have an itch account at the time of the purchase but it says that you don't need one in order to receive the gift.
Tell the person who bought it to reach out to support with the email they used to do the purchase: https://itch.io/support
Consider the possibility that your friend misspelled your email. It’s also possible that they made a mistake and actually didn’t buy the game. They can check with whatever service they used: If their service didn’t bill them for the game that is a strong indicator that something went wrong on your friend’s end… ;)