App Service Domain was detached/deleted from my resource group and is no more accessible

Getting your nameservers back to Azure DNS

You can do this without the Azure resource. Your App Service Domains are registered through GoDaddy behind the scenes, and there's an account under the email on your Azure subscription even though Azure never shows it to you. Run a password recovery at GoDaddy's Domain Control Center against that address. If you get in, repoint the nameservers to your Azure DNS zone from there.

Getting the resource back into your resource group

That one is a support ticket. When the Azure resource goes but the registration survives, the domain management object stays orphaned against your subscription, and only Microsoft can clear it so the resource can be recreated. It isn't a portal action. Worth raising it as a migration issue rather than a deletion, since that's what actually happened and it points them at the right thing.

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