<Snip>
Defects
During the warranty period described in the Device Specific Addendum, if the Device is or becomes defective through no fault of your own, please contact Google Play Support. Subject to the Device warranty, Google, in its sole discretion, may offer a replacement Device or may refer you to the applicable manufacturer of the Device for warranty support. If Google chooses to provide you with a replacement Device, you agree that Google may exchange the defective Device with either a new or refurbished Device. If you do not return the defective Device within 21 days from the date the replacement Device is delivered to you, you authorize Google to charge your Google Wallet account for the replacement Device, not to exceed the amount paid for the original Device. Nothing in this section affects your legal rights.
<Snip>
I know this is an old thread but I found it today as I was considering buying a (new sealed in box) product on eBay.
The above quote from Google Play's policy, while accurate, does not actually say anything about the original purchaser being the only one who can use the warranty.
In fact the only relevant section I can find is:
"You may only purchase Devices for your personal use. You may not commercially resell any Device, but
you may give the Device as a gift. Recipients of gifts
may need to open and maintain a Google Wallet account in order to receive any support offered by Google. These Terms apply to any gift recipient."
This, along with the rest of policy (i.e. discretionary replacement/repair/return to manufacturer) indicates that you don't need the original receipt or any other proof of purchase but you may need a Google Wallet account. I am not sure if the device needs to be tied to your account via the IMEI or if it can only be tied to one account. The latter doesn't seem fair, since you might gift your old/duplicate phone/tablet to someone else after buying/being gifted a new one, but I am aware that warranties are often heavily slanted against the consumer.
It also appears that the manufacturer's warranty is independent of Google Play's policy - so if you couldn't get Google Play to facilitate then you would have to deal with the manufacturer directly and the outcome would depend on their policy.