I found in Iphone 5 on the bus and it has a passcode lock on it. How do it unlock it?

I've tried plugging it into my computer and restoring it using itunes but the passcode lock doesn't allow me to do so. Any tips?

Go to the shop and unlock it

Return it to the owner some how. Its to much work to get past that passcode and getting your own number.

1: Turn off iPhone - Hold down the Sleep/Wake button for a few seconds until the red slider appears, then slide the red slider. Ignore this step if your iPhone is already off.
2: Press and hold down the Home button for about 10 seconds until a yellow triangle with a text which says Please Connect to iTunes appears.

NEXT

1: Plug the iPhone into Mac or Windows PC. Release the button if you haven't.
2: Run and open iTunes if it's not already opened yet.
3: iTunes will prompt a message that says iTunes has detected an iPhone in recovery mode. Click OK.
4: You will be taken to the iPhone pane. Then, click on Restore.
5: Wait for the full restoration process to complete, and the iPhone will be back to the original settings state as when it left the manufacturing factory.

However, I would highly recommend that you try to return the phone to its owner