Hmm. Interesting input.

Especially cause now I am very much in doubt whether there was ever a mnemonic seed.

When were these introduced?

I do know that I should have backed the wallet.dat but there is really nothing to do about this.

On a side note, I would never seek help from someone explicitly offering to retrieve lost btc passphrases.

I happen to know and trust someone who may want to do this experiment with me, pro-bono.

I just need to gather as much info as I possibly can as to when, how, what client so on and so forth. Cause she hasn't a clue.

When/if I decide to actually try this. I'll report back.  

EDIT: I see that the seed's were introduced in 2013. So I couldn't have had that.
This leaves me thinking that my idea is kind doomed from the start.