Activation Lock Apple ID not existing anymore

Hello everybody!

I've just bought a used iPhone 5S (32GB) off of a local and trusted website, that's similar to eBay, and the person was trying to sell an iPhone 5S. I bought it, and there was one thing he didn't tell me before buying it. It had his old iCloud account on it, and when I got the phone, he claimed that he deleted his iCloud account. I reinstalled iPhone OS onto it, put it back to factory settings, and it's "Activation Locked". But it's locked to an account that he told me he deleted, so I don't know what to do. Can anyone help me with my problem? Also if there are Apple employees here, I'd really like to contact one here, if he/she can help me out with it!

Thanks in advance!

Sent from my iPhone