it could be possible that you have an altcoin's private key.
Unlikely:
blockchain.com show it's base58 (p2pkh) format and shows some small balance.
the address is a valid bitcoin address, but it could be possible that the additional information was from another wallet like an altcoin private key written beside this bitcoin address.
I guess I might have used BIP38 encrypt with aditional password. How to verify that?
if it were then bitaddress.org would have asked you to also enter your password. and also your string would have started with 6P
here is an example and the password is "hello"
6PYPsQUESqNqtM9NMYcUBn3tKDMkF8QE8E8N4dFdp1K7tyFG1yn1jjiS9K