In some parts of this world taking something that isn't you're usually means cutting off the hand. ....
Also a great answer. "stepping off the sidewalk" versus "metal detecting" (which involves "taking" something) are two different beasts. Right ? I totally get what you are saying.
Yes: It's true, while md'ing can be done in a non-intrusive way (leaving no trace), yet .... it's true, we "take" and "remove" things. Each of which we can find laws that prohibit, and are worse than merely "walking" there.
Then are you aware that "take" and "remove" laws are equally in PUBLIC land laws/codes/ordinances too ? For example: Take a look at any park or beach you go to. Find the rules of use. And I'll bet you dollars to donuts that you'll find prohibitions on "remove" , "take" , "harvest", etc... Such that no one helps himself to the the park benches, or starts harvesting sod or sand for commercial sale, etc.... Could the rule/law be applied to an individual coin ? YES INDEED.
Not saying that your observation isn't utterly correct. Just saying: If we start down that path of defining md'ing as "take" "steal", etc.... : You would equally loose all public ground too.
But again: This all goes back to one's definition of "vacant" or "abandoned" , etc.... I can think of vacant lots in my town , where a bldg. burned down or was demolished in the 1950s. And has sat vacant ever since (neighborhood too blighted for any economic re-built or development). And so, they sit, with shopping carts strewn about them. A short-cut trail across them. And: If you looked up on the assessor's office parcel maps: Owned by someone 100+ miles away (the descendants of the original owners, who have long since moved away from the blight).