If the game is not appearing on the HOME Menu, it can be redownloaded at no cost using the same Nintendo Account that originally purchased the game.
You may need to select All Software to view your full list of downloaded games.
Scroll through the HOME Menu to see if the game is already downloaded to your system.
When a game is listed as Purchased in the Nintendo eShop, it means the game has already been purchased by a Nintendo Account using the same Nintendo Switch console as their primary console.