Hi,
pulling the key out while it is running isn't that uncommon, a worn barrel after50 years, but the first thing to check is the key back in the Lock position?
In theory the ignition you have cut out when the key went back past Aux, but sometimes people, me included, wire it up wrong and ignition goes down the Aux position as well.
If the barrel is in the Lock position use a multimeter on Ohms to check wiring coming out of the ignition switch. Undo the four wire plug and put one probe on the terminal with the fat brown wire and the other probe on each of the other three wires/terminals. You should get no circuit, but you may find one of the white wires is creating a circuit and if so you have an issue inside the barrel assembly.
If that checks out okay, then you may have something finding power to the coil that shouldn't be, so start at the '+' side of the coil, with the ignition off, and see if you have 12v +.
Or maybe just leave out some cookies and milk and see if it is fixed for you tomorrow morning.
Terry