Death to all thieves or failing that just cut their thieving hands off,,,,,,,,,
Rant over sorry to hear of your recent event, thats bad luck! Best to have a lock of some sort on the bike , just to deter the scum stains that thinks its ok to lay their mitts on someone elses stuff.
I guess the vermin have shorted the wires from the starter switch, trace the wires from the loom on the handlebars and hopefully you will find their mod.