This happened to me yesterday. At 10:06 AM I received an email from amazon telling me they processed my ‘return’ and that my $0.99 would be returned for Animal Farm. With my Kindle at home, I opened my Kindle iPhone App and watched as Animal Farm disappeared from my home screen. I went to the archive and saw the flash as it disappeared there as well.
I called their customer support and talked to the guy about it for a bit. It sounds like the only way to keep this from happening is to keep the Kindle radio always turned off.
Later that afternoon, at 3:13 PM, I got another email that 1984 suffered the same fate. I even got my $3.20 refunded.
Weird thing was… I checked Amazon later and 1984 was back and available for $3.19.