Actually, yes you can get the password back from BI.
Export the registry data (or simply view it with regedit), and navigate to the configuration area for your camera.
E.g.
HKEY_LOCAL_MACHINE\SOFTWARE\Perspective Software\Blue Iris\Cameras\Porch
Copy the
ippw value and paste it here:
https://www.base64decode.org/
Press the decode button and it should tell you your stored password.
For example, if I set a password of
12345, ippw has the value
MTIzNDU= and the website I linked above can decode it back to 12345.