Is it not possible to mount the agents via the Workstation ? Then view the data in Historic Mode to get back to the period you are interested in ?
For the alert notification, one way to do it would be using a calculator based alert, similar to the recommended way to capture disconnected JVMs.
If you create a calculator monitoring Heap Memory In Use, then set it to fire once whenever the value is > 0. That should tell you when the JVM has started up. Create another alert when the same metric is <0, again to fire once. That should tell you when it has stopped reporting to Wily.