Comment 41 for bug 484252

Faced the same problem and it erased a whole priceless 120 GB of backup drive instead of a single partition. Fortunately like Daniel (https://bugs.launchpad.net/ubuntu/+source/usb-creator/+bug/484252/comments/16), I was lucky enough to be able to retrieve back the partition table using testdisk and consequently got my data back again.

This is a very critical bug I see, I don't know about this specific tool's progress in further versions.