In reply to Lord of Starkness:
There was a famous case where Amazon were contacted by the publishers of Orwell's 1984 with a cease and desist order as they had not bought the rights to sell it. With the Digital Rights Management feature, they turned off (deleted) everybody's copy overnight which had the same effect as you're seeing.
I'm not saying that has or hasn't happened this time, but it is something to be aware of. Buying and e-book isn't the same as owning it.
If I were you, I'd e-mail Kindle support and ask for help. They should know common bugs and be able to check your account on the server.