There does not seem to be a disassembly guide available for your notebook and best I could find was videos which you no doubt have already seen.
As said previously your BIOS chip is detecting the optical drive so appears to be ok and replacing the CMOS battery will not imo make any difference with the present HDD not being detected, trying an alternative known good HDD is the only way to determine if it is a fault with the present HDD or a problem with the BIOS.
If there was a problem with the pins you would not be able to mount the HDD using the live media so the drive must have a good contact with the MB, the same goes for the drive being recognised in a USB adaptor.So, how to check pins?
As said previously your BIOS chip is detecting the optical drive so appears to be ok and replacing the CMOS battery will not imo make any difference with the present HDD not being detected, trying an alternative known good HDD is the only way to determine if it is a fault with the present HDD or a problem with the BIOS.