The ship that crashed in Blackmoor was the Beagle; as for the engine, you're probably thinking of the Nucleus of the Spheres, which was the artifact left over from the ship millenia later on Mystara. It's kind of murky whether it was the Beagle itself or another device which caused the Great Rain of Fire which wiped out Blackmoor- by this time, Blackmoor had already become highly technological from what they'd taken and learned from the ship. So depending on the Mystaran source it was either the Beagle or something that Blackmoor themselves had made later.
Given the way Mystara was developed, the history and whatnot was subject to change over the years. Also, thematically, there's sort of two Blackmoors- one is the recently published, fantasy campaign setting with slight sci-fi overtures. The other is the mythic history, high-tech empire that left all kinds of weird devices and artifacts all over Mystara. So there's Blackmoor's IC history to confuse things, as well as the history of the setting and how it's handled in various worlds.
These were the Blacklore elves, who were present in the latter-day, high tech Blackmoor Mark II that I mentioned above. When Blackmoor was destroyed, the elves were taken to the Hollow World to preserve their culture, which is what the Hollow World was for.
As a side note, every so often we see threads of people who want to use D20 Modern or Future to update a world to present level tech, like FR Modern or whatever. Seems to me like Blackmoor would be the best choice to have both fantasy and sci-fantasy time periods (hint hint, Dustin

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