[mikebo]

I don't think you're familiar with how Multi AZ RDS works: http://aws.amazon.com/rds/faqs/#36

The whole point is to protect you from problems in one AZ by keeping a hot standby in another AZ. It doesn't matter whether it's due to EBS, power, etc. This is one of the primary reason to use RDS instead of running MySQL yourself on an instance.

[res0nat0r]

Yes...what also sounds plausible is that since this was an EBS outage that the underlying EBS volume wasn't detected as being unavailable (if it in fact did become unavilable) so no failover to your other RDS server was initiated.