In this case the reason you can't get it with a seed might be caused by seed divergence. As of Beta 1, I believe it was, something partially broke seeding such that runs may not always be identical, depending on random actions that might've been taken, but I'm not sure what or where. They are often repeatable, but not 100%. Too bad because for the first few years it worked perfectly xD
These things are really hard to track down in such a large game, and I asked for help in solving it last year but it's a rather big project and no one took up the request so I'll have to try to solve it myself one day, but this could take a very long time...
I say this because that encounter is completely random.
To help in this case I would need both your save one entering that map, and nuzcraft's... Then I might be able to find what's different, but even then it's quite tough. Sucks!
