Mmh, interesting. I will make him open a new wallet with electrum using the legacy or p2sh-segwit option then. Although I doubt that's going to do anything given that the address with the money starts with bc1 so it should be segwit.
When you send Bitcoin, you often end up with change (read here to understand why)... HD wallets adhering to the BIP44 spec generate a separate group of addresses for this purpose... as per the derivation path format:
Because of the way Electrum works, when you put the seed in, it actually derives the master private and public keys at the account level... and stores those in the wallet file. So it's basically "hiding" the m/84'/0'/0' part from you... and you need to use the m/0/x and m/1/y paths to find the receive and change addresses, respectively.
That fact that you can see "used" addresses on the m/1/0 path, indicates that the address you have found is a "change" address... you should be able to see other active addresses on the same public key using m/0/0
Having said that... something seems REALLY off here:
That is technically a "change" address, but the sending address in the transaction that it received coins from is an old Legacy address... so... either:
1. The Coinbase Wallet App is setup to ALWAYS use SegWit change addresses (regardless of sending address type)
or
2. The Coinbase Wallet App gave out a "change" address as a receive address
Can you ask your friend if he recognises either of the "1" addresses in this transaction: https://www.blockchain.com/btc/tx/ac14d45dfa3bfdc5ab026643ab214d2821fe245b401ace85fe01d29583285735
15FfborJuBXicY93ymX9QPf9nrQ6mHeH3k
and
1JuYbj6L8UCtBF5cJHFPaNb3kJEJcPXN8h
Are either of these addresses his? or does he remember receiving from 15FfborJuBXicY93ymX9QPf9nrQ6mHeH3k or sending to 1JuYbj6L8UCtBF5cJHFPaNb3kJEJcPXN8h?
He gave me 2 different zpub public keys because I made him open different wallets on electrum trying to manually change the derivation path with some that I found online.
Now I'll ask him to open a legacy wallet too, maybe that's the issue, no idea.
I'll ask him your question regarding those 2 addresses as well. Thanks