@DaveR: I did a brief (some might say perfunctory) search before I posted this and didn’t see an appropriately titled feature request.
I, as a newbie, made all the wrong choices, posted here (My 2nd forum topic!) - and you gave the solution!
Since then, I’ve seen too many other people make the same mistakes. While using @TIG’s Default Layer Geometry (to fix) and Layer Watcher (to keep from making the mistakes again) are good solutions, I think the origin of the problem lies within SketchUp - and SketchUp should fix it as I suggested.