Your windows 10 key is on the MS Servers (digital entitlement) if you activated windows 10 when you upgraded.The windows 8 key cannot be retrieved by the user. Win 10 upgrade is done with windows 8.1 running and the key is recognized by the installer. Here are MS instructions--

Activating Windows 10 after a hardware configuration change

I understand that if you make major upgrades you have to reactivate but I did no upgrades at all.

Ok .. so if I revert to windows 8 will I be able to do the free upgrade again?

You should not have to do that. Resetting the cmos must have been the major change. 

See this from MS--

If you upgraded to Windows 10 using the free upgrade offer and then made significant hardware changes to your device, such as replacing the motherboard, Windows 10 might no longer be activated. For help on how to activate your device, contact customer support.

More--

windows.microsoft.com/.../activation-in-windows-10

IMHO, doing anything in BIOS/UEFI shouldn't cause Windows 10 to need reactivation.  I would say there is a fault in the OS itself and would call Microsoft.  They are providing free technical support on Windows 10 for a while.  

I have contacted support and they tell me that I need to provide the original Win 8 product key and I can't do that because it was injected in the motherboard and from everything I have read and have been told I can't get it :(

Still get blocked :(

I just can't believe that there is nothing that can be done.. I made absolutely no hardware changes.. All I did was reseat memory.. cards and reset cmos trying to get the pc to start up.. which it did.

I've been running Windows 10 Pro, also the free upgrade, over the last month or so on my 8700 XPS. I've made no physical changes to the PC, nor have I done anything in BIOS/UEFI. The other morning, upon powering on the PC, Windows 10 is no longer activated. The event logs showed several error messages related to licensing. I tried the "activate Windows" from the system menu, and it showed the product key as blocked.

Anyway, here is what worked for me to reactivate Windows.

From an elevated command prompt (right click on start menu), type: slmgr /ato

Is the computer working OK otherwise? If all is working--You can reinstall 8.1 and do the win 10 upgrade again. Here is a way to do it using the Create Media Tool--

http://windows.microsoft.com/en-us/windows-8/create-reset-refresh-media 

You must choose the same version of windows 8 that came on the computer so it matches the key. The iso file burned to dvd is better since you can save it for future use. Once you reinstall you must check to see if win 8 is activated before doing the upgrade to win 10.

You skip entering the activation key and the installer should read the embedded one. Read all the directions on this page carefully--

 http://windows.microsoft.com/en-us/windows-10/activation-in-windows-10