I removed one of my plug wires (left the plug in and put in a different plug) to check for spark due to a no start condition.

Had key on, used starter solenoid to crank from under hood. Spark plug was in the boot, sitting atop one of the air intake hoses. Truck started and that plug was sparking away, not grounded to anything. Keep in mind truck wouldn't start at all moments before this as well.

My truck is acting insane, there are crazy things going on. Won't start, leave the key on for a bit, go back and it will start. Will die after running a bit, same thing, hard to get back started. Sometimes (rarely) it will just fire right up and not die for the whole day.

 

So you SAW it happen, and you're asking if it can happen??? Yes, the voltage generated by the coil is enough to jump a small gap (or 3), so it was jumping from the plug to the nearest ground.