I'm not certain, but I think I recall that blockchain.info in the past used to supply a mnemonic that you could use to recover your password.
The modern 12 word mnemonic at blockchain.info is for a wallet seed.
If I'm right (and my memory of 2014 blockchain.info is pretty foggy, so I certainly may not be), then you'd need to find a copy of the algorithm they used back in 2014 for converting a password into a mnemonic, and then you'd might be able to access that wallet.
Well there's code on github but that's beyond me. Ill try emailing blockchain.info. Theres probably bugger all in there, but I need to know