How to unlock a 16GB iphone?

So I work at a library, and someone lost their iPhone, but it was locked with a 4-digit passcode.

I tried putting in a couple, now it says "iPhone is disabled, connect to iTunes"

But when I connect it, it says I can't restore it because it was password locked.

How do I get any sort of identification to return it? (like what its phone number is for example, we have a database that could tell me whose it was if I knew what its number was)

Alternatively, if you could tell me how to unlock or restore it, that would work too.