I know they are lost for good. I still can't understand how it happened. I've already been contacted by someone pretending to be from PayBack-LTD. They provided a lot of explanations, some YouTube channels of their company etc. They want to pay $1500 upfront to recover my funds and 10% of the recovered amount. If nothing is recovered, then the $1500 paid is not refundable.
They are scammers. Don't trust them, if you don't want to lose more money. Bitcoin transactions are irreversible and no one can recover your fund.
So I would say the seed was somehow stolen, used to recover the wallet, and transfer the funds.
This is my guess too. Someone probably had access to your seed phrase and made that transaction manaully.
If your wallet had been hacked, it wouldn't take 2 days to steal the fund.