OpenSea is one of the most familiar marketplaces so you'll likely want to see your NFT when you view your OpenSea profile.
As of Oct 2021, OpenSea hides Polygon NFTs from unverified collections by default (source). Generally this means that for any new Polygon NFT project with low trade volume, you won't immediately see the NFT in your collection. This behavior is unfortunately out of Paper's control at this time.
How do I unhide the NFT?
You can log into OpenSea and unhide your "Hidden" collection items at any time.
Log into OpenSea
If you purchased to a Paper Wallet, see How do I log in to OpenSea?
If you purchased to a non-Paper wallet, please follow that wallet's instructions.
Go to your Profile
Go to your Hidden tab
Select More options
Confirm the Unhide action.
You will be prompted to "sign" a request with your wallet. This does not cost any funds and is only used to validate that you are the owner of this wallet.
That's it! Your NFT should now be shown on your public collection page.
How else can I confirm I have the NFT?
Fortunately all data on the blockchain is public, so you can use other tools to see your NFT. You can log in to your Paper Wallet to view your purchases or search for your wallet address on Polygonscan and check the Tokens dropdown: