Dreadblades Hidden Appearance Issue

[Macanam]

I'm struggling to find any information on this, but hopefully someone here will know.
I unlocked the hidden Thunderfury-ish appearance for the dreadblades on my rogue about 2 months ago. I was looking to unlock some extra colour variants for it, and to see if I'd already made some progress I went to the rogue order hall with my dreadblades equipped, only to find that the hidden appearance is still hidden on the appearance tab so I can't actually set my dreadblades to use the appearance.
This is NOT a transmog issue - I can use the normal colour appearance as a transmog on my BFA weapons.

Have I missed something? I was under the impression that all appearances and colours were still available other than mage tower and M+ 15. And since the base appearance is unlocked it should absolutely be appearing on the dreadblades appearance tab.

Any ideas?

Thanks

[Department]

From the wording of your post, this isn't the issue but it's the only thing I can think of:

Are you sure it's the base appearance you have unlocked and not one of the progression ones like 30 legion dungeons? If you don't have the base appearance, but have unlocked a variant through progression from another spec's hidden appearance, you won't see the row at the weapon altar.

[Macanam]

From the wording of your post, this isn't the issue but it's the only thing I can think of:

Are you sure it's the base appearance you have unlocked and not one of the progression ones like 30 legion dungeons? If you don't have the base appearance, but have unlocked a variant through progression from another spec's hidden appearance, you won't see the row at the weapon altar.

Turns out you're right. I actually unlocked it on a different rogue. /Facepalm. Time to go unlock it on this one I guess, thanks for your "wrong" solution!