Found an iPhone 4, how to unlock it and keep the data?

I found an iPhone 4 a few days ago but nobody seems to have rang or text the phone so I don't know who it belongs to, there's a password on the phone and after a few failed attempts I still couldn't unlock it.

Are there any ways to unlock it but still keep the data? I google'd how to unlock it but really the only way that seems possible is to put it in "DFU Mode" however this wipes all the data from the phone and that would be useless to me if I'm trying to return it.

I can't go to an Apple store to unlock it as the nearest one is quite a bit out of the way and my parents won't want to drive me just to get the phone unlocked for somebody they don't even know (harsh but true)

I'd like to return the phone to the owner so if anybody knows any way to unlock it without deleting all of the data it would be much appreciated!

Thanks

Added (1). About the police thing, I'm not above trying to hand it in to the police but from past experience matters like these are rarely seen to, I've had friends and family hand things like phones in but months down the line they still haven't been seen to.

If I had a "hidden agenda" I'm pretty sure I would just do the DFU Mode thing and wipe the phone completely before I keep it for myself, but seeing as I have the iPhone 5 this would be a pointless thing to do

If you genuinely want to return the phone and not keep it, why don't you simply hand it in to the police. I'm pretty sure that if I lost such a phone I'd report it. Some might suggest you have a hidden agenda here.

Well try holding down the home button and see if you have siri if you do then ask her these to see if you can get her to tell you who owned the iPhone: "Show me my notes"
"Who am I ( she should give the iPhone users info)"
"What's moms email"
What's Dads phone number"
Or ask her "what can I ask you?" She should give you a list and try to get info from there.

Like suggested before, try using Siri to find out something about the owner.

BUT DO NOT return it to police. I have done this before, they just keep it for some time and if no one comes to get it, they keep it…

If you can't find out anything about the owner, do a reset and sell it on ebay, or give it to a friend.

Can you not go to the place you found it and ask there? Someone may have gone in and left alternative contact details.