Aluneth transmog not available — artifact previously unlocked on the same class and spec

I no longer have access to the Aluneth transmog appearance for Arcane Mage, even though I previously unlocked and used the artifact on another character.

Context:

  • I fully completed the artifact questline for Aluneth on an Arcane Mage during Legion.
  • A couple of months ago, I created a new Arcane Mage, while the original Mage still existed.
  • I played the new Mage for around 2 months, then deleted the old one.
  • Unfortunately, I did not check whether the Aluneth transmog was available before deleting the old character.
  • Now the transmog appearance is missing.

I expected that, since both characters coexisted for a while, and Aluneth was unlocked on the old one, the appearance would be saved account-wide, and usable on any arcane Mage.

Please investigate whether the Aluneth appearance can be restored in this case - I would really like to use it on my new Mage.
Thank you!