@pastacode , I'm having the same problem with the same model dell (9360). For me, after I go into the F12 one-time-boot menu, click the flash update option, select the XPS_9360_2.5.1.exe from my thumbdrive, and click "Begin Flash Update" the machine immediately reboots and I'm taken back to the bitlocker recovery key screen. How were you able to start the flashing process??

Disable Secure boot. 

Unfortunately I get the message " ME firmware end update failed error 0x000002236. Anyone know what that means? 

If you have disabled secureboot 

In this video use the USB method to recover BIOS with latest file 

https://www.dell.com/support/kbdoc/en-us/000132453/how-to-recover-the-bios-on-a-dell-computer-or-tabletvv

Once BIOS update is done 

Enable secureboot again

BTW 

Have you checked if you have recovery key  at www.onedrive.com/recoverykey

Now here's something truly odd:  I just rechecked (as in: it being the first thing I did yesterday when the problem began and in since having checked several times while trying to fix the issue)  using the link you posted, and voila! now all the recovery keys are there.  So am back in!

I have been using another laptop to access info and of course checked that one straight away yesterday too. Bitlocker function had been activated (not by me...) with no recovery key in the microsoft account (as said, did check several times). And now, it's been activated (not by me) and this time the recovery key is listed in the microsoft account.  Hope this is not confusing....certainly weird.

So first, thank you so much for your help, and posting the www.onedrive.com/recoverykey link which made me go check one more time. Maybe it's specifically using the onedrive access rather than just logging on to the microsoft account that has made the difference.  

For others out there with the recovery key problem, there is hope. And really great help here on this forum. Thanks again.

I am running into the same issue of being locked out by bitlocker after the BIOS update, I never set up bitlocker and was in fact unaware of its existence at all until this issue arose, consequently I don't have a recovery key and one doesn't exist when I check my microsoft account etc.

Regarding the potential fix of downloading an old BIOS version and installing it through a USB drive, do I need a program installed on the USB drive to do this or will it be able to run the downloaded BIOS from the USB drive by itself. Thank you for any help you can provide. I am only semi computer literate when it comes to unexpected issues like this. I need access to my files on my laptop etc and reinstalling windows and wiping my hard drive are not an option. 

Thank you Dell!

I've lost all my data on my Dell XPS 13 9360 as well.

Thank you for turning on this bitlocker on my new laptop without notifying me.

Now I don't have bitlocker recovery key as I didn't know it was turned on.

The key is not stored in my Microsoft account as I didn't use one for login to windows.

In attempt to remove trigger for bitlocker recovery mode I tried all available BIOS versions (starting from 2.5.1 till 2.16.0) with no luck.

So, all data has been lost now. 

BTW - it happened 19-aug-2021 as well. It looks like Really Good Update came these days for poor XPS 9360 owners. Is there any way to roll it back?

Now I'm starting to think that guys creating ransomware are not that bad, at least they are sending you decryption key for money.

Just tried it again for BIOS 2.5.1. (BTW this is earliest compatible)

The only difference from what I did before(trying ALL versions of BIOS) - toggling on-off before BIOS updated.

Didn't help. It's still in recovery mode.

The only gleam of hope I see now - I have an error in BIOS update:

"ME Firmware update end update failed error 0x00002236"

Actually I have it for every BIOS update, but may be this is important and if I could avoid this error - bitlocker recovery mode will go off?

I have same message.

But it means that just part of BIOS failed to update.

Hasn't bitlocker recovery gone after this update?