I'm in the exact same boat. Hadn't played the game for a bit, loaded it up and all my gear was at level 1 with all Deluxe Edition items missing. Checked for Add-On content, says I don't own any, nothing in the forge.
I started trying things. I verified files, unchecked dlc, loaded the game, and checked for Add Ons. They actually showed up! (Completely unleveled, though, which is another frustration). But after I re-equipped them, I checked for Add Ons again, out of curiosity, and it said I didn't own any Add Ons, it saw them once, why not twice? Closing and re-loading the game, my items were gone again.
I then tried a few more times to recreate them showing back up. For a bit, I thought they were gone for good. But I finally got them to show, and I was able to save and load a couple times and they were still available.
So something is bugged here, but try going into the DLC page for the game in Steam and uncheck the deluxe dlc, load the game, leave game, recheck them, then load the game. See if they come back for you. It does suck that ALL of the resources I put into these items to level them up are gone, but I wasn't very far in the game, so these are still better than what I had (especially since it gave me level 1 base items when these got removed).
A customer that paid extra for these items shouldn't go through this, so I would suggest the Devs figure out why this is broken, but at least they can come back. Also a shame there is no way to recover the resources put into leveling these up....quite frustrating.