I can't re-download a game that I've previously purchased

On March 20th 2018 I purchased Sea of Thieves on the Xbox Companion App on my computer. I have achievements from that day and I have a bank statement open on another tab that's proof that I bought this game. Towards the end of last year I upgraded to
a new computer and recently have been having an itch to play the game again so I got back on my account but the game doesn't exist anymore, it is no longer in my "my games" tab. I have gone through my account settings and it even says I have no purchases
on this account from the Microsoft store. This is impossible since I have a bank statement to prove otherwise and I have achievements for the game unlocked. How can I possibly have achievements for a game if I've never owned it? Sea of Thieves has only
done a "friends play free" week once as far as I can find and all of the achievements I've gotten have been from different dates that don't correspond with a free to play week. If I have purchase proof of the game and an account with achievements from said
game on it, how come I no longer have that game? I have paid for a product, please allow me to use that product.

:)