With manual awnings if you do not lock it down that can happen. not sure how hard it is to override the lock
With motorized awnings there is both a brake and the gearing of the motor. it has never happened. HOWEVER. if you are worried there are many types of clamps you can apply high as you can reach on the awning arms provided there is a gap behind the thing. Or you could even drill through (Awning closed) and put in a pin.. One of the square-oish Sring pins sold for tow bar attachment should work
Or you can get those in all sorts of sizes at Tractor Supply and other Farm & Fleet type places. this is a bolt, with a spring attached to the head. the other end of the spring SNAPS over the other end of the bolt to lock, VERY secure. Just make sure you don't drill through where the gas shock is if you have that kind of awning.
I use safety ties on mine.