Don't worry. Walter is ultimately a super-unimportant character. If he's all you lost, you aren't missing jack. There's even another place to turn in scrap that you might find later, heh.
I really wish they'd address this, because as far as I'm concerned, it's the only thing keeping the game from being nearly perfect. There's that and the sometimes shitty pathfinding, which has on a couple of occasions given me some annoyance. Other than that, most anything you can throw at the game will be a nitpick at best.
And Cobra, I'd say no. It's a shitty bug, but it doesn't seem to happen to everyone, and even if it does there's so much more of the game to try. Unpredictability in this big a game is an unfortunate fact of life, and while I'm not sure why this bug wasn't caught, I haven't heard about much else going wrong, and my own 90+ hour experience, as I said before, had little more than a couple crashes and the one experience with the bug in question. And that's basically it.