I'm not sure if you understand the magnitude of possibilities of OP's starting point. The sheer vastness of possible twelve words combinations is unfeasible to check and exhaust. You either don't have enough energy and/or time to check any possible combination of his "puzzle" situation.

It doesn't even help very much that you don't have to deep check every permutation, because the last word of BIP39 recovery words contains a partial SHA-256 checksum. You can exclude all permutation of words that fail the partial checksum test in the last word. But that's still only a rather marginal optimization, because you still have to check at least for a proper checksum before going further.

Without sensible clues how his "puzzle" was constructed, which the OP apparently doesn't have anymore, it's not likely to significantly reduce the amount of possible word combinations. The sample space is very very likely simply too large.

So, how can you say "it's very possible" when in very likely fact it's simply the opposite? "It could be a lengthy process...", yes indeed, if you have hundreds or thousands of years, guesstimated, you'll definitely have to take your time.  

I'm not sure if you understand the magnitude of possibilities of OP's starting point. The sheer vastness of possible twelve words combinations is unfeasible to check and exhaust. You either don't have enough energy and/or time to check any possible combination of his "puzzle".

It doesn't even help very much that you don't have to deep check every permutation, because the last word of BIP39 recovery words contains a partial SHA-256 checksum. You can exclude all permutation of words that fail the partial checksum test in the last word. But that's still only a rather marginal optimization, because you still have to check at least for a proper checksum before going further.

Without sensible clues how his "puzzle" was constructed, which the OP apparently doesn't have anymore, it's not likely to significantly reduce the amount of possible word combinations. The sample space is very very likely simply too large.

So, how can you say "it's very possible" when in very likely fact it's simply the opposite? "It could be a lengthy process...", yes indeed, if you have hundreds or thousands of years, guesstimated, you'll definitely have to take your time.