It's possible a wire may have come off the mag coil but not likely. Its more likely that your ignition circuit is grounded. Test your mag wires for continuity, then see if the mag is throwing any voltage while rotating the crankshaft. Make sure the kill switch, tether cord button, or ignition switch wiring aren't shorting the circuit to ground. Check the ignition coil's 2 input wires for continuity. One of the 2 wires should be grounded. If the ignition system is working, you should see a nice blue spark when you pull the engine over while checking the plugs. Be sure to hold the plug you are testing against a head bolt or other good ground. If you still get nothing, then I suggest you check your points as they may be dirty (or rusty). New points & condenser are easy to find, but you'll need a flywheel puller to get at them. It is possible that the ignition coil or mag coil could be faulty internally, but not likely - if you just recently had a spark. When they do fail, its usually after being very hot.
Good luck