No password or passcode

Hi

I hope for your sake that the device is not locked to an iCloud account otherwise you're out of luck.

First i would recommend calling the local police station just to check to see if anyone has reported it stolen.

After that turn the device off, hold the home button down and plug it into a computer with iTunes on it and running, after a few moments it will recognise the device and it will ask you to either update or restore the device, pick restore, follow the prompts, it will take a while as it will download the OS for it. once it has finished the device should be ready to set up as a new device, if it is locked to an iCloud account it will ask you for the account information and currently theres no way around it that I am aware of.

good luck