my smoothwall, I tracked something down to
/proc/bus/usb

ls -l shows two files, both zero length,
Code:
[root@smoothwall usb]# ls -l
total 0
dr-xr-xr-x    1 root     root            0 Apr 25 10:25 001/
-r--r--r--    1 root     root            0 Apr 25 10:25 devices
-r--r--r--    1 root     root            0 Apr 25 10:25 drivers
but you can
cat devices
and it will show you details from the usb bus about what is there.
might show someinteresting details, might show some more of where it is in the
.dev.sda1 mode of things