Nope.
You need to authenticate any platform's account to add it or delete it from Bungie.net as a security feature.
Bungie will not step in as this is a personal matter.
Maybe Steam can help you.
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I’ve already got into contact with Steam and what’s funny is the fact that they have tried redirecting me to the Bungie Support/Help Forum.
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That means they can not restore or provide a authentication for you. Bungie will not do anything at a guess due to account security.