I bought Skyrim with Dawnguard and Dragonborn DLCs several years back. I completed the Dawnguard, got most of the achievements (and even have some screenshots) but sometime within the last * years, my Dawnguard DLC has dissappeared. Steam shows no record of me having it. And trying to get a support ticket put in has been a dead end, it wont let me proceed since its "not on my account". (User : SDX** ) Please look into this.
I trust that Steam Software will make this right and come up with a resolution that is fair.