No bill --- no guarantee

After several requests (live and via Amazon employees), it was impossible to receive an invoice for this article:
Consequence: if the disc comes to let go, it will be impossible to prove the purchase. Moreover, no bill also implies no VAT to be deducted (for a professional).
In short, a purchase should be avoided for a gain of a few euros ...

PS: I did not want to return it to the risk of not having anything at all: invoice and drive.