Sorry about the outage, you can recreate the problem by doing the following:
1) Decide to move your site to a shiny new set-up on Amazon
2) Decide to move your dns to another DNS provider
3) Setup shiny new environment
4) Change the ip address with the original provider to the new IP
5) Unlock the domains for transfers
6) Immediately go to the new DNS provider and submit a transfer request
7) Crap! a race condition exists and the transfer request interrupted the dns record update mid change and the DNS is not locked for 5 days in Limbo with no record.
8) Beg / plead and chase up both DNS companies for Days with each telling you the other has to change things there end to no avail
9) Ping your back online on your new shiny servers
Reasons for the change happening in the first place will be announced very shortly.