I think I owe you an apology, Crimtide. I took your response to my inquiry of if you had these items when the system went live in the affirmative, and re-reading - you really didn't say.
While I am indeed seeing some Vengeful here - I don't think it's the pieces you are looking for - do you see pieces of this on your mail wearing characters?
When the collection system went live, it mainly keyed off of some things that records where records were retained - like quests - and what you had at the time. Some of those needed to be added. My suggestion to do a full reset UI or toggle the filters was based on a presumption that you did have these at that time - and that is my fault, again - I am terribly sorry - I should have dug into this deeper at the time.
Going back into the records of the character you transferred, I'm seeing no trace of the specific ones you mentioned. That means it must have been quite some time ago. I went back one further, to the iteration of your priest in 2010 - and while I found furious, relentless and deadly gladiator gear from 2009 - that too had disappeared by the time you left Stormreaver.
2008 the incarnation on Azjol-Nerub I could find Mooncloth versions of the gloves and hood in your inventory. When you transfer a character, it leaves a snapshot behind, that's really the only reason we can see that far back in your case - all the transfers :), but that's only as the character was as it was transferred. If the items weren't present during the transfer, that information is gone.
You still have a ticket open, I'd recommend you leave that open and let another set of eyes sift through this. Again, I am so very sorry to have spoken based on a presumption.
I server transferred last week to get ready for Mythic raiding with some friends.. when I did, ALL of my xmog gear except for what I have found in Legion has gone missing.. ALL OF IT!
I have almost 300 days play time on this character alone.. 7,000 HOURS! On just this toon alone!!! I have 4 @ 110 now, and several others between 85-100.. I can't imagine how much time I have in this game across all the toons..
I was an officer/raidlead in a realm first guild for years!!! But I am being told by a GM that I never soulbound anything and that's why it isn't showing up?
I opened a ticket, the GM responded with the typical scripted response saying I'm out of luck. He tells me that it's because of your new system, and then suggest the reason why is that I never equipped the loot, soulbound it, etc...
Explain to me how I raided for 10 years (2004-2014) and I have no XMOG gear after I server xfer? Explain to me how I had full glad sets from BC through Cataclysm and nothing is there?
Your GM tells me that I have none of that gear, because I never soulbound it!
All my tier sets, GONE! All my PVP sets, GONE! All my epic xmogs, GONE!
I am furious..