Talk about extraordinary bad luck----
Actually, that could be a piece of extreme good fortune. I'm not certain of what German law is on this subject, but, if something with no clear delineation of ownership falls from the sky and onto your property, don't you now own it?
And if you own it, wouldn't it be possible to sell said piece of meteorite to any museum, university or scientific entity that was willing to pay for it for the purposes of research?
And if someone is willing to pay for it, you could probably turn a tidy sum for it, I would imagine.