[sc_rufctr]

You're not being paranoid. Something triggered your garage door and it wasn't you.

Maybe the guy in the box truck had a remote code rolling device of some sort and was trying to gain access to your garage?
(the smart thing to do would be not to park in front of the garage you're trying to open)

I've heard rumours that there are coding reading devices that can defeat the security.
Is it possible someone "read" your remote while you were using it?
Predicting the next code is complex but there are devices that keep guessing until they solve it.

FYI: There are robotic safe crackers now. It can take up to a month to open a safe but it's a mathematical certainty.