Take a look at some findings:
(id is either slot or item)
Code:
local isTransmogrified, canTransmogrify, cannotTransmogrifyReason, hasPending, hasUndo, visibleItemID, textureName = GetTransmogrifySlotInfo(id)
GameTooltip:SetTransmogrifyItem(id)
I do not see any changes done to the inspection code, so maybe you can't extract what the original item looks like? Hmm...
I mean, we will see but I am certain that perhaps the itemlink contains something, because if you link it to a friend won't they be able to equip it on themselves and check it out? Or will the item keep the original view instead of the custom one?