Is it possible to find or wipe a lost iPod Touch if Find My iPod was not previously activated?
In short, it is, unfortunately not possible to activate Find my iPod on a device that is no longer in your possession.

If Find My iPod was actually enabled, you can go to www.icloud.com and login to your Apple ID to see more information on the device and to set it so that the data is erased after being connected to the internet (if it wasn't already). If you log in to the iCloud web portal and the iPod isn't shown, then it was likely not enabled. In this situation, it would be impossible to activate it.

Remember, either way, the iPod must be connected to the internet in order for any changes to be made.