Hello,
On the bitlocker ask screen, it has the bitlocker key ID, the first section of the ID is what you want to use to find the key in your account. If it is not there, then it means it was not saved to your account.
I wish I could share good news, but the truth is no one can get you the bitlocker key, including Microsoft staff/support. https://support.microsoft.com/en-us/windows/find-your-bitlocker-recovery-key-6b71ad27-0b89-ea08-f143-056f5ab347d6 The link here says:"Important: Microsoft Support doesn't have the ability to retrieve, provide, or recreate a lost BitLocker recovery key."
If you set it up with school or work account, it is worth checking here as well https://aka.ms/aadrecoverykey sign in with your work/school email credential in that case.
When you set up your computer after reinstallation, did you use a different account to set it up by chance?