The "NIC still broadcasted" part is what gets people every time, they assume no lights means no network. Ran into the same thing with an old HP printer that had wake on LAN turned on, the power button was off but the thing kept grabbing its IP and fighting a new workstation. What worked for me was checking the switch and router ARP tables instead of running around unplugging stuff, since the MAC address pointed right at the printer maker and saved me about three hours. If I can't do that, I just look at the link light on the switch port, because a dead device won't hold a link. Fax machines and printers from that era are the worst for this since half of them never fully power down the network chip.