I hate to say this but it might be due to the recent duplicating of items. Unless you can prove you bought the items from the CS (which you can through the diamond buying reports) then I do not think most have a case. Hopefully this can be taken care of quickly though.
To my knowledge, this is not related to that issue. Rest assured that we will also investigate all reports to the best of our ability.
I thought that of the duping also. I bought them from my diamond seller. Think it shows on records when you gift someone 140 of the same item?
Support may require the name of the player that sent these items to you, but provided you removed them from the mail and they entered your character's inventory, there should be a clear log of how many you obtained and how many were used.
I see no difficulties so far in making sure all of these items are returned. Please, however, answer any questions that support asks you completely, and to the best of your ability.
Even a general answer ("I got them sometime in March", for example) is better than "I don't know."