Something similar happened to me, honking didn’t help in my case. It might have here, it might have not.
From the time I realized that the other driver hadn’t noticed I was there to when he bumped into me, I only had a couple of seconds, I actually lost time by honking.
Now that’s just silly. If the truck driver is able to see you (Not that he will, just that he can), then you are in a place where the truck is not likely to back into.
Agreed.