I have been searching the forums but haven't found an answer to this specific problem. I recently installed an external port for both data and power for an SATA drive. It is not eSATA; it uses the same cables and plugs as the motherboard, and in effect is just like hooking it directly to the motherboard and internal power supply, just extended outside the case. I was using it to do mirror backups of the inside drive, and it was working fine. I mistakenly plugged the external drive into the external plug for power and the plug for data without powering down the computer, and nothing came on. The drive did not spool up and the drive was not recognized by the system. After that, the drive would not work at all; no spin up, no recognition at BIOS level. I have swapped it with the main drive without result; it is now just dead.
Did I wreck the drive by plugging it into the system while the computer was powered on?
It sure seems like it, but I don't know why. It almost seems like you got extremely unlucky, because I have an external enclosure which I use for the same thing, and plugging it in when the computer is running has not been a problem for me. My enclosure does differ from yours in that it has it's own wall wart, but still the only problem that I have is that it is not recognized because I don't have a built in e-sata port on my mobo. I suppose that maybe the drive got more inrush current than it should have. Do any of the parts on the bottom look blown?
Plugging in the data connection will have no effect. It is the power connection which we think surged and blew something. The only other possibility that I can think of is that you somehow zapped it with static electricity, but the likelihood of that happening exactly when you did the first thing seem remote.
For what it's worth, I plugged it in just as the computer was rebooting to the BIOS screen, so maybe it was a surge of some kind. It could also just be coincidence and bad luck. But the good luck is that it is still under warranty, and off it went this morning to the hard drive fountain of youth.