only have a backup if you have been pressing F10 after you do a save.
F10 copies all your xml files. I use it all the time.
One word of caution! F10 does NOT back up your current session. If you have been editing for 6 hours, pressing F10 every 5 minutes but you have not pressed save in the last 6 hours, we are just backing up the last saved xml file. If there is a crash, you will be going back to teh xml file from 6 hours ago.
My suggestion is press F10 after you press save. This will ensure you have many copies of your working sequence.