Hello there[url=https://media.giphy.com/media/KOVlHmbBA09XO/giphy.gif],[/url]
In order to unlink an account, you must be able to authenticate it, which means you must be able to log into it. Bungie cannot forcibly de-link it.
[b]I would suggest contacting the platform concerning recovering the platform account.[/b]
If you are unable to gain access to your account, then you will not be able to unlink it from your current Bungie.net profile.
You must be able to authenticate to an account in order to disable Cross-Save, enable Cross-Save, or Link or Unlink an account from your Bungie.net profile.
You'll need to work with Stadia to recover the account.