Link to SharePoint Online site doesn't show up in Groups, Teams, SharePoint Admin center.

Matthew Carter  Mostly it happens if that site is associated with the private channel so you will not be able to find that in the Admin center and also no group associated with this, but recently there is a new update which most of the tenant has got you are now able to see the private channels child site in the admin center.

if you believe that is not a child site, then you maybe be able to search the site using the display name, also the same will have group email, and Teams created which all should have a same display name and you can find it in any of the places either in Teams, Groups, or Sharepoint Admins centers.