If you do an FDISK -L you will see the following. See if you see the USB stick.
root@ICS-MythTV:~# fdisk -l
Disk /dev/sda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders, total 234441648 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00040a95
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 226260991 113129472 83 Linux
/dev/sda2 226263038 234440703 4088833 5 Extended
/dev/sda5 226263040 234440703 4088832 82 Linux swap / Solaris
root@ICS-MythTV:~#