Domain Controller's Forward Lookup Zone Disappeared

Our Domain Controller's Forward Lookup Zone for our Active Directory domain just disappeared. Our backup Domain Controller had a copy of the zone, but since the primary server was accessible but had no records, the standard failover from primary to secondary did not occur, and RPC requests simply failed.

I restarted the primary, and the zone seemed to come back, but I have 2 questions:

1. How is it possible for the zone on our primary domain controller to disappear, when it's entirely local to that machine?
2. When the zone disappeared, the failover did not occur because the server itself was still reachable. Could we have added the secondary domain controller's IP address to the primary domain controller's forwarding list to prevent the failure from happening? (As I see it, when the primary queried for a record and couldn't find it, it would in theory forward the request to the secondary domain controller, which would have resolved the record, still having a copy of the forward lookup zone in tact)

Thanks...