I'm very glad you'll be OK. I guess that situation is a little bit similar to when I'm riding a bicycle and a car passes. It's easy to assume it's safe at that point and move out into the lane for a left turn, for example, but it's always possible that there's a second car behind the one that passed, that I couldn't see in my mirror because of the first car. So I have to hesitate and look again before assuming it's clear.
While you couldn't see the 2nd car, you could have assumed one was there until proven otherwise. Mind you, I'm not saying I couldn't have made the same mistake, but at least now that you've brought up the problem, maybe it will be on my mind if I'm in that situation.
It's not clear to go unless you can see that it's clear to go.
