Hi D_BOT,
Have you used this drive in any other PC, where you might have accidently locked it? If you connect back to the original PC, it might auto-unlock on that machine.
BitLocker never-ever get created and implemented by its own. Applying BitLocker on any system requires several steps then only it gets implemented.
If it has been implemented and you don't know the key then there is no way to get the key and you might need to perform refresh, reset or reinstall windows. The key or the Recovery drive is the only way to access your drive back.
More information, read this article:
BitLocker frequently asked questions (FAQ)
https://technet.microsoft.com/en-us/itpro/windows/keep-secure/bitlocker-frequently-asked-questions
Note: That applies to Windows 10.
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