Maybe it hasn't crossed over the pond yet.
It's a sign usually deployed by left-over women as a kind of personal motto.
It always strikes me as a kind of display of personal conciliation. And then the next thought that occurs is "So what: it is not my concern.".
This.
Only about one in twenty of recorded 'crime' is ever solved. I don't know whether that includes posting a tweet (aka non-crime hate incident). That's recorded crime (if they'll let you record a crime).
Same view as you: got turned away with that same phrase "civil matter, sir".
I'm guessing that the real figure is maybe 1 in 100 at best. I'm sure I saw a pod cast of that undercover detective (Pete(r) B-something?) who was evicted from the Met who said the figure was in that ball park. Can't find it or remember his name. Bah!