Not a silly question at all.
I often wondered that before I got my first turbine endorsement.
Most turbine helicopters do not have an ignition key aside from the Hughes/MD range mentioned above.
Basically, you jump in, turn on the battery and hit the starter button and away you go. The only thing that stops hoons running away with your aircraft is the door lock (that requires a key). Most pilots may disconnect the battery if the aircraft is left un-attended.
You may have remembered some years ago a JetRanger being started up by some idiots in Orange, NSW after breaking into it. I think he actually got it started and got into the "hover" before it all turned pear shaped for him. I think the aircraft was the Electricity Commission machine.
Hope that helps.
