iPhone 5 w/ iOS 6 passcode locked and in airplane mode. What do i do?

I purchased a used iPhone 5 with iOS6 installed online for cash and can't use. Here are the details:

-iPhone 5, iOS6 installed
-Phone is in airplane mode
-Phone has a passcode that I don't know

The guy I bought it from online won't answer/return my emails I feel like I may have been ripped off. I tried to restore it by holding the home button while plugging it into my iTunes, then it proceeded to restore it but halfway through I got an error message saying:

"there was a problem downloading the software for the iPhone. The network connection timed out. Make sure network settings are correct and your network is active."

All I want to know is if there is any way I can get use out of the phone. It has the iOS6 software with a passcode lock and is in airplane mode. The seller is long gone and the phone is useless to me. I spent a couple hundred bucks on a paperweight.

Is there any way I can get some type of use from this phone? I found a discussion about a similar issue someone else had: https://discussions.apple.com/thread/5491891

Would going into DFU help in my case as it did in the other folk's case?

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