He could try to recall the word order, but it would still be inaccurate, I guess.
Can you be more specific here? Are you talking about the order of the other 8 words, or the position of the four unknown ones?
Crunching the numbers, if he is missing four words AND doesn't know the order of any of the words, then you are looking at something like 2
73 possible combinations. This would require renting cloud computing to solve, and would be prohibitively expensive unless the wallet contained a
significant amount of coins.
What exactly do you know about the order of the known words and the missing words?