I think the scalehouses only "expect" to get a sampling of the trucks on the road. Most times, they don't know whether you came in, or not.
Last time I 'missed' a scale, I got off at the next exit, reversed my direction for about 7 miles, and approached the scales for the second time. The sign then said, CLOSED. Was I the idiot I felt like? I don't think so.
I drove by with a clear conscinece. They could come after me if they wanted, but they didn't..... EITHER time.
My advice is.... if you "accidentally" blow by a scale.... keep on truckin'!
But, at least hit the brakes as you go by! That way, they know you thought about it!