I think I accidentally vendored or destroyed the Raw Singing Citrine this week. This item doesnt’t appear in the Restore Service either…
Is there anything I can do about this situation?
You should be able to buy a replacement from the vendors
Not so sure about that, the Raw SInging is the upgrade item, not one of the socketable ones…
Search your inventory just to be sure, incl your bank if you visited it, just to make sure you didn´t just misplace it after all… and if there really is none there, a support ticket might be the solution. 
Blizzard doesn’t restore items anymore. Just ask the 1100+ guilds who lost there entire guild banks, with nothing being restored.
If an item can’t be restored via UI or bought back from vendor - tough luck.
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