Great work on the pics!
Ok, so the bluetooth is an internal module. No, won't ask to dismantle the laptop to get at it.
When you changed the hard drive did you reinstall windows? and if so, did you install chipset drivers
? They are needed to run non-standard stuff.
Btw, when you installed drivers did you run their hw vendor detection utilities? it's the"Need to know the hardware on your system to choose the right drivers?
" in the driver
Do you have "Unknown Devices" in Device Manager? (should be under "Other Devices")
If yes, follow this tutorial
to manually identify the device.
Another try is downloading the bootable Iso file of this
, burn it to a disk or on an EMPTY USB drive with rufus
and boot from it.
Then look in the PCI devices list if it says something about Atheros, Broadcom or bluetooth.
The empty port is a mini-pcie port. Can house anything with a mini pci-e port. GPS, bluetooth, wifi, TV tuner cards. Does NOT run SSDs unless they clearly state that they run on a mini pci-e port. Most try to trick you saying pci-e SSD because they have the same form factor and size, but they actually use another kind of port (that resembles mini PCI-e).
If nothing else works, I speculate that the empty slot contained the bluetooth card that was removed by someone.