If you do not have Proof of Postage or Notification from BT that the item was received then there is nothing that can be done.
This thread has been answered and is now going round in circles.
These things happen. Don't think you have anything to reprimand yourself about.
I do belt and braces when I sent my tv box and router back. I took photos of the model and serial numbers from the rating labels and photos of the post office receipts. Luckily in both cases I received the confirmation emails from BT that they had received them.
@Martynwithywrote:
"it is highly unlikely (almost impossible) that the mail service just threw it away."
When I retired from work, just over 4 years ago, I had to post some forms to start claiming my company pension.
Because of the importance of the documents I chose to send them by Special Delivery, which apparently means they are tracked every step of their journey and were "guaranteed" to arrive by 1pm the next day.
Royal Mail lost the package and had to refund me.
Luckily, (foresight? / cynicism? / experience?), I had taken a scan of the documents, so filling out the replacements was fairly easy. I sent them back, again by Special Delivery, and this time they arrived safely.
Unfortunately, the pension provider then mislaid them! 😖
Bizarrely, Royal Mail then found the "lost" original package and delivered it, so I got my pension in the end.
I was seriously considering driving the 300 mile round trip to deliver a third set of documents personally! 😀
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