But if you recall your days with computers you only reach a state of backup with 2 or more copies. It sounds like you were driving some unicycle with no spares and crashed.
Time Machine (Snow Leopard) deleted all my old backups and then, and only then, informed me it did not have enough space to complete the backup in progress. True, I was perhaps naive to think TM would treat a clone of a volume as if it were the same volume and not a whole new backup, but still, a rational person would think TM would calculate the disk space it needs and warn the user before nuking all old backups. But the only option I find in TM prefs is "Notify after old backups are deleted." I assume those backups are now irretrievable, since I did not back up the backups, in an implicit infinite backup regress.
Carramba! If the same people who designed TM designed altimeters, the pilot would get an alarm after the plane has crashed. Sometimes we mere mortals are aghast at how dumb smart people can be.