Found a I phone 4

In Puerto Rico on vacation I found this I phone 4.There is a passcode lock.How do I find the owner? and if the owner is not found can I use it and upgrade from my 3gs?

Reply 1 : Found a I phone 4

How about handing it in to the nearest Police Station?

Mark

Reply 2 : Found a I phone 4

Apple seems to track us better than Facebook.