I don't see them blaming byuu. I see them giving practical advice for ways that might reduce the chances of this happening in the future. That's different from "this is your fault, not ours."

The eBay listing indicates this may be theft, not just plain loss. Have they told USPS about this? And I don't mean telling their no-doubt powerless social media team on Twitter, I mean reporting it to the postal inspectors:

https://postalinspectors.uspis.gov/investigations/MailFraud/...

I (thankfully) have no experience with them, but I have heard that they are not people you want to mess with.