1. On your desktop browser, open the page https://opensea.io
2. Click on More, and select Hidden.
3. Click on the 3 dots '...' for more options, and select Unhide.
4. They will prompt you to select the NFT(s) you wish to unhide. Click on your desired NFT, and click on 'Unhide' at the bottom of the screen.
5. Then, you will be be able to see it under the Collected tab.
Need additional help? Please contact MetaMask Customer Service directly.