They aren’t showing on your character, this is a bug that affects multiple items and is mildly annoying. But I think the game still marks those appearances as “learned” despite not showing up as a learned appearance.
If they were deleted from your actual account, you’d have to repurchase the items because they simply won’t reappear.
so I think the issue is in the actual transmog feature rather than the store or “receipt” of the appearance
There’s a reason I said “basically.” The semantics are irrelevant. The point is that it’s gone from both collections and on the character’s stamped transmog.