rescue data from usb disk - don't want to format

You should try to obtain an image of your drive with

ddrescue

(see the GNU ddrescue Manual on how to use this tool). Drives should not be mounted. For your machine a command similar to this may be able to create an image of the memory stick:

sudo ddrescue -f -n /dev/sdb /home/earthling/rescue.dd /home/earthling/logfile.dd

After sucess we can now try to recover files from this image without any further damage or risk to the data that still reside untouched on your USB drive.

We may try to repair the filesystem with tools depending on the format we had there (ext4, NTFS, FAT32,...?).

Alternatively photorec from the

testdisk

suite you obviously already had installed may be able to recover individual files (but not filenames) from such an image. See the nice PhotoRec Tutorial for details.

photorec /home/earthling/rescue.dd