Found an iPhone what should I do?

Last weekend I was clubbing and I looked down on the dance floor and I picked up an Iphone 4S that I found. I put it in my bag and forgot about it, I then realised I had missed calls from various people that appear on the home screen. If you don't know, then you can ring back people so I rang back a number that hadn't been added to a contact so I could see the number and they didn't answer. I then couldn't ring any other numbers because they had disappeared off the screen. The phone was locked and at the time I was having a good night out so decided to sort it out in the morning and contact them then. The phone ran out of battery almost immediately after I had rang the number so I couldn't answer any other calls that might've came through
In the morning I charged the phone but all the missed calls had disappeared cause the phone had ran out of battery. As the background of the phone was a picture of a girl and a boy, I figured that the phone would belong to one of them. I thought I remembered some one called Jessica ringing the phone so I searched 'Jessica' on Facebook, obviously this was no use because there are millions of people called Jessica. Then I decided to inbox the club on Facebook but they haven't replied. I also searched through the photos that were taken throughout the night trying to recognize someone from the wallpaper in the photos but I was unsuccessful. I was going to take it to the police but since it is a popular club for people from all around England, they probably won't be from where I'm from. Although they might think it was an invasion of their privacy I tried to unlock the phone, I did this because I thought they wouldn't mind as long as they got their phone back. I was going to contact a number from their contact list but I couldn't guess it. Basically, I'm wondering if there's any way to use the phone to see contacts or anything like this? I really want to get their phone back to them because I know how I would feel if I lost my phone! Help please! They have blocked the contract so no texts can come through or anything like that.

How about you turn it into the provider, they should be able to find the owner and get it returned.

Like the guy said above, you should go through their contacts and look for people like "mom", "dad", and call them on your own phone. If you scroll up to the top on the contact list there should be something saying who owns the phone (their name).

The carrier of the phone (check it by the SIM card used) shall be able to find the original owner by the SIM card number (ICCID) or IMEI number of the phone. If you were not able to unlock the phone, contact the original carrier and see what they can do. It is the fastest and easiest way in my opinion.