The query above returns the proper object_id. But in the process of going through this exercise, I found that I had overlooked something...
If a package is being installed through the install.xml facility, the admin user object does not yet exist. The admin user account is created after all core packages and install.xml packages have been installed. I guess one way to lick this problem would be to establish the admin user object_id in the acs_magic_objects table. Or, I could create my own magic object and then later, after the admin user exists, change ownership of my object to the admin user.
My question is this: is there an established and/or supported method for packages to allocate a magic object?