The hindsight-prescriptive comments here focus on backing up, and that's a sensible practice. But there was another kind of damage done here, to the man's identity, location and voice. His blog and his email address were his public persona. He used his blog and his address as identity, and as his channel of communication with followers, other artists, and I assume most of his general online communication. That person…
Just look at Google's hostility towards maintaining standardized IMAP/SMTP support for third party mail clients. Google Apps and Office 365 would drop IMAP access to their services in a heartbeat if they could.
Furthermore a lot of our online interactions are moving from open formats like Usenet, IRC, XMPP and SMTP/IMAP to closed off walled gardens like Twitter, Instagram and Facebook.
This artist's online presence could have been entirely based on Instagram and Twitter for example and I bet many (younger than I) folks nowadays do eschew email for other forms of communication.
I don't think self sufficiency in communication is a problem the end user can be realistically expected to solve. It's up to engineers and technology stake holders to try and push us back to a more open way of using these apps and provide standards based communication.
I don't know how the heck we'll do that - I don't see any user pressure for companies to even try, but news like this troubles me and I think it's going to get much worse before people realize their data isn't their own and push for it to get better.