You don't.
Read Carefully: [url]http://www.bungie.net/en/View/bungie/eula[/url]
You are LICENSING the rights to play Destiny.
Any content that may have been on the Disc at time of purchase is not yours it belongs to Bungie and Activision.
Therefore you were never cheated out of any content as it was not yours.
If this is unacceptable to you there was a 30 day refund policy granted to you in the terms & conditions that you probably didn't read. If it has been more than 30 days you have no one to blame but yourself.
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"But we bought DLC but it was already on disk! Wine wine wine" Do you even know what dlc means? "DownLoadable Content." Nope. Disk Locked Content.