If the output of lsusb were nothing, it may mean that the USB controller is not enabled on the server BIOS.
Look mine:
# lsusb
Bus 06 Device 02: ID 0624:de11 Avocent Corp.
Bus 06 Device 01: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 05 Device 02: ID 046b:ff10 American Megatrends, Inc.
Bus 05 Device 01: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 02 Device 04: ID 413c:a101 Dell Computer Corp.
Bus 02 Device 01: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 07 Device 01: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 04 Device 01: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 03 Device 01: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 01 Device 01: ID 1d6b:0002 Linux Foundation 2.0 root hub
There is no USB device attached, but I can see the USB hubs and etc (this is an ESXi 5.1 server).