I gotta go with the majority here. I think you are overreacting.

This wasn't discrimination or bigotry. If they wanted to violate ADA, they would have never built those handicapped spaces in the first place. No, this was a case of someone being careless or selfish. I'm not sure how the truck was oriented--he may not have even realized he was blocking handicapped spaces if he came in when it was dark!

I think you should have notified the manager via drive through and your problem would have disappeared pretty quickly.

Also, I'm surprised that the lobby was open at such an hour. Usually they just have drive through open.