I have a thunderbolt to ethernet adapter and functional network at home and it wasn't able to do what they did. Holding option didn't bring up anything and internet recovery did nothing, wired or wireless. Call it whatever you want but there was simply no way possible for a user to restore this device. To me that is a brick.
It's just a netboot server with Installs and known good OS environments. You could have done it yourself with an external hard drive... not that going in was a bad thing to do. They certainly fixed your issue.