Ok no sueing.
Is the best advice to just let it go? Is there ANYTHING we can do?
I mean -- here's the thing: people make mistakes. Sometimes people make horrifically disastrous mistakes that cause horrible outcomes. Clearly in this case although there wasn't an actual horrible outcome (thank goodness), things were bad enough that both you and your wife can picture the way the outcomes would have been horrible and that is, itself, horrible in its own way
(Also, horrible things happen that are no one's fault, and that too is horrible. I know you are really upset about what happened and I understand why, but ... I am living where we have seen a number of people die in the past week because of the hurricane, and possibly more to come, and well, its just horrible. If you want the world to be a just place, well -- it's not. I'm not saying that I don't think anyone did anything wrong in this case because I do think someone did, but ... not every horrible (or near-horrible) thing that happens, has a solution. That's hard to accept, and it can be particularly hard to accept as a parent, but it's still true...)
I personally have been upset about a lot of stuff in the past several years and mostly when I get really mad about something that's happened, I give money to a group that tries to prevent whatever I'm upset about having happened, from happening. That may not be exactly applicable/relevant in this case, but I think if I were you and if you can afford to do so, I might make a contribution to an organization that helps needy parents and families. You could even find out if there's a way to donate to a group that helps families that can't afford them, get carseats for their kids. Life is dangerous. People do dumb things. Sometimes bad things happen even when people don't do dumb things. We can't change those realities but we can make differences around the margins sometimes.