Cloning Operation Seemed to Clone to More then one Destination Drive

I would be grateful if anyone could share their insight as to what was going on when I performed a drive clone last night.
Acronis True Image 2014 clone performed of non-partitioned 128GB SSD (C drive containing Win 7 Pro OS) to a 512GB SSD (because disk was becoming full). The operation seemed to go seemlessly using the automatic settings. On completion it shut down the PC so I removed the 128GB SSD source drive and rebooted using the new (500GB SSD) destination drive. An examination of 'My Computer' now showed that one of my other drives (F drive - 128 GB SSD) had also been cloned - with all data on it overwritten. I was confident that I had performed the clone correctly - although (perhaps foolishly) hadn't made a back-up of the F drive. Fearing the worst, I thought there was nothing to lose by trying to return the machine to its original configuration - so I swapped the new destination drive with the old source drive expecting to see the same picture. However, with the old drive back in place there was no sign that the F drive has been touched. (All the old data is still there and is accessible). Needless to say I have now backed-up the F drive. (BTW - two HDDs in the machine did not appear to have undergone any changes).
So, with my old C drive back in the machine the F drive is as before, but with the new (cloned) C drive in the machine - the F drive's data appears to have been overwritten.
Any ideas what may have happened?
Many thanks
Chris