Swedish court rules meteorite should stay with owner of property where it landed
apnews.com
apnews.com
UK law gives the finder and landowner market price for the treasure between them though. That makes the economics rather different than what it would be if they got nothing.
Nitpick about "steal" in your hypothetical scenario: taking the meteorite wouldn't be stealing until someone claims the meteorite or until the state comes up with an "XYZ party gets ownership" rule in the first place (XYZ being the owner of the landing location in this case.)
Presumably 50 miles but I haven't read the law.