It did finally show up in our PHD, but it showed up as having been resolved:
"[08:52 AM PDT] Between 7:49AM PDT and 8:27AM PDT EC2 experienced elevated API errors for instance related APIs in a single Availability Zone in the US-EAST-1 region. Existing instances were not affected. The issue has been resolved and the service is operating normally."
It was in US-EAST-1C.