My sister has come to me with a bizarre story.
1. She tells me the bitcoin I owed her and sent to her in December of 2017 is somehow unaccessible to them. She's not asking me to replace it but was hoping I could help her recover it.
2. At the time they generated an address out of their trezor and emailed it to me.
3. I sent them the bitcoin.
4. I guess they confirmed receipt by checking the address on chain rather then going back to the safety deposit box for their trezor??? I can try and get more details from her regarding this but that is my understanding at the moment.
5. In January 2020 they moved all their bitcoin off the trezor onto Coinbase (temporarily until they could get another custody solution set up, which they have now done and the coin is back in their possession). It was during this move to Coinbase that they noticed the coin I sent to them in December of 2017 was NOT in their trezor balance. My sister claims they could see it in some separate "legacy wallet" showing up on the trezor interface??? It is not clear to me exactly what she is talking about and I don't think they have any screen shots. But I can interrogate her further on this if necessary.
6. She reached out to me for help and I suggested they put their seed phrase into an electrum wallet and the coin should show up.
7. She tells me they did this and while it shows all their tx history of their coin... it does not show the missing coin.
8. She and her husband have finally thrown in the towel and have given up. They have offered me a small monetary reward if I can recover the coin for them.
9. They have given me their old trezor, which I told them wasn't necessary but they gave it to me anyway, along with both sets of seed phrases that they have ever used with it and their pin numbers (Something I also told them was unneccessary but they gave them to me anyway)
10. I took one of my own trezors and factory reset it. Entered both sets of seed phrases (one at a time of course). Both sets of seed phrases show ZERO coin in the trezor.
11. I tried going into the "secret wallet" on the trezor by using their pin numbers as a password, thinking maybe they accidentally entered the pin in the password field and created a secret wallet when they sent me the bitcoin address. But none of the pin numbers used as a password for the secret wallet produce a wallet with anything in it. I can ask them if they ever used a password with their trezor...
12. They also gave me a copy of the email with the bitcoin address in it. I could post it but don't see any point in doing so at this time. I mention it only to say I did check the block explorer and the address does indeed contain the coin I sent them in December of 2017. So it DOES exist and is sitting out there on the blockchain.
13. When questioned where they acquired the address from that they sent me... they are both very certain that they got it from their trezor. If that is true I would think the coin should show up in the trezor account when restored?
So I am trying to decide what I need to do next? I wondered if I could build and submit a tx to the blockchain requesting the transfer of the coin from that address to one of my addresses and somehow provide the private key (The mnemonic seed phrase they gave me) as my credentials for having the authority to spend the coin and would the blockchain move the coin if indeed the private key was correct?
But if the private key is correct the coin should show up in the trezor? So before I spend a lot of time trying that I am open to any other ideas I should try? Any other questions I should grill my sister on? I did put the 2nd seed phrase into an electrum wallet of my own and it does indeed show all their tx history and does cover the time frame in which I did send them the coin. So I believe the 2nd seed is the correct one. But the electrum wallet is indeed empty. So I am baffled as to what they might have done? As in where they got the address from?
Thank you so much for taking the time to read. I'm open to ideas...