So I'm guessing here, they forgot the passcode? Find My iPhone has nothing to do with forgotten passcode or accessing the phone.
The only way to bypass the passcode it to restore the phone on the computer you normally sync to and restore the backup. However, it appears from what you have typed here, that the computer your normally sync to is broken. The only thing you can do is to use another computer to restore, however you will restore as a new device, since you cannot access the old one. Also, since it is locked, you cannot create a backup either. Not a good situation to be in.