Wow.
I've been working in the web hosting business for 15 years, and the explanation you've been given is pure B.S. The host is either lying or really, really stupid. Back in 2006, the host I work for was on the receiving end of the biggest DDoS anyone at our upstream providers (two of the world's largest) had ever seen, and we lost no customer data.
Unfortunately, even if your host was honest about the cause of the data loss, that doesn't help you in a situation like this. You can piece together your site through caches and archives, but hopefully everyone reading this will think twice about their hosts. This is really a subject for a different thread, but it just kills me to see people trusting their hard work to incompetents and jerkoffs, and that's what 99% of the "hosts" out there are. This kind of amateur hour stuff really pisses me off, and I'm sorry that some of you had to suffer because of those fools.