I bought an iPhone 6s Plus today from eBay. Will I still have the 1 year warranty?

I didn't pre-order, couldn't wait 4 weeks to get the phone from Apple, so I ordered from an eBay seller. This eBay seller preordered the iPhone online and received it in the post today, and has sent it to me unopened. As we speak it's with Royal Mail now on it's way to me.

I hope I'll never need it, but if anything were to go wrong with the phone, would I be covered under the 1 year warranty if I don't have the receipt, digital or otherwise?

If not, what information should I ask the seller to give me so that I will be covered?