I don't know for sure, but I'm willing to bet that your finger was on one of the buttons as soon as the device recognized a correctly inserted battery.
Folks don't realize that the device needs power to recognize the "five clicks on sequence." And there are some devices (like the Pico 75) that have to be five-clicked off to perform certain functions like flipping the screen display 180 degrees. I think one of the Sigelei devices needs a battery door opened while holding a button to do a factory reset, or closed while doing so. Some phones also need arcane little sequences.
Somewhere out there, there's a mod with a program in it that is waiting for a user to insert a battery while holding three buttons and a tongue in the 510. That will activate Skynet and summon this guy.