Deleted USB Partion

Raw file system means that there was some error that did damage the file system information.
I understand that you wanted to format the partition, not to recover data.
I guess that probably the partition table is damaged.
In this case, you can use GParted  to delete the existing partition table by creating a new one ("msdos" type).
If you encounter problems like "unknown" errors, you can try to wipe out the entire pendrive space from the terminal window,
using the command "dd" to write 0 (zero) to every byte. Then you can retry.

Be careful with the dd command. Specifying the wrong drive will delete its content with no recovery hope.

If you are interested in recovering any data from the pendrive, you can try "testdisk" (for partition table and partition information) and "photorec" for individual file recovery.
testdisk is included in the GParted live cd/usb. photorec is available at its web site:
http://www.cgsecurity.org/wiki/PhotoRec
It is recommended to make a clone of the pendrive to another one of same or larger capacity, to be able to make multiple recovery attempts with no risk for the original content.