India Post — empty box delivered

Address:

Jodhpur, Rajasthan, 342003

I have purchased a Lenovo K8 Note mobile from Amazon Site on 16/03/2018 (Invoice Number: DEL[protected] for Rs.11999/-. While using the mobile i found that it was discharging very Fast, then i talked to Amazon Technical team and they tested the mobile online and found that there was a problem in the mobile. They told to return the mobile for replacement. Since my job was transferred from Chittaurgarh to Jodhpur, they told to send via courier or preferably by Indian Post.
I sent the mobile via Indian Post on 28/03/2018 from Jodhpur and same was delivered on 02/04/2018 (As per Indian Post tracking details). Amazon informed me on 07/04/2018 that the box received at their end is empty.