Is it a miracle that my hard drive has recovered?

Hello, - just reposting this as a proper question, because I'd like some views:

my (maxtor cased external) seagate 7200.11 500gb hard drive stop being read a few days back and I finally narrowed it down to a faulty PCB or need for firmware from seagate. So I downloaded and made a bootable CD and opened my PC to disconnect my good internal hard drive and reboot from cd with the faulty hard drive now connected to M'Board.
So I screwed up and disconnected the dvd drive and connected the faulty drive instead. So I now have the original good hard drive still there and a second hard drive in place of the DVD drive.
So without realising this I switched on the PC and at that point realised my mistake - however CHKDSK kicked in and repaired my hard drive - which now works beautifully. Is this a fluke? I couldn't run anything on the hard drive when it was faulty - I was getting the 'do you want to format the drive' message in Microsft 7
I guess my question is, why did this happen (the hard drive accepting and being repaired by chkdsk) and why is there no suggestion of this method from Seagate or forums who look at just PCB's, upgrading firmware, sending hd off to recovery experts or chucking it in the bin