Thanks, I need to try that.
Currently I am using ...
--
https://wow.gamepedia.com/API_GetCursorInfo
local infoType, cursorItemID, cursorItemLink = GetCursorInfo();
... because the item is on the cursor.
I am also using the "GET_ITEM_INFO_RECEIVED" event and the "CHAT_MSG_LOOT" messages to get hold of item strings, therefore the items may not in my bags at all.
Therefore for the tooltip I use
GameTooltip:SetOwner(UIParent,"ANCHOR_NONE");
GameTooltip:SetHyperlink(itemLink);