Okay, I'm told that the code that determine if a scheduled job is missed, and executes immediately if the job's options specify that it should do so, is only executed when the service is started. Therefore, when the system returns from hibernation/suspend modes the service is already running and so this code is not exercised.
For those who are using the Windows scheduler to wake up their machine to take backups they could have the scheduler run a .cmd script which bounces (stop and starts) the shadowprotect service. This in turn would cause the backup to occur (if one was missed during suspension). The script would just have two lines:
net stop "ShadowProtect Service"
net start "ShadowProtect Service"