So  nostr:npub1mfndvgwstwm604jvrt07p6nyy898mdsdzzyumx9sdn8u6r4za4uqck6f8v posted "mother" as the 12th word, yet there's not even an "R" in his letter list. 

This is disingenuous. I was under the impression his seed phrase was only 3 and 4 letter words, consisting of only the letters copied.

Not the first 3-4 letters of any length words.

This is impossible. He might as well not even have given letters. Total waste of time. I regret even engaging.