Is it possible to recover from a partial clone?

I made an uncharacteristic error using Comodo Backup which was seriously dumb. I was in a bit of a fog and not think clearly when I started a cloning process to an external drive that contained data. It only ran for a few seconds before I stopped it, but by then it had written a new partition and marked it as a primary partition.

I would like to know if I can undo the primary partition or whether the NTSF file indexes have been damaged too seriously. I want to try recovering files which may not be overwritten since most of the disk is now listed as free space.

I don’t know why I was so stupid, normally I am more alert. However, I’d like to know why Comodo did not incorporate a warning to the effect that a cloning operation wipes out any data on the disk. There should be a window displayed to that effect warning anyone attempting a cloning process and asking the user if he/she is sure he/she wants to proceed.

I have an app for retrieving data at a low level but it is indicating an 8 hour recovery time on my 500 gig external drive. Other high level recovery apps wont look beyond the new partition.