OK, I have experienced this as well. Nature faction. All research complete. Last completed were faction level 3 and Leadership 3.

I suspect my problem is that because this is my second tribe, I completed the bath and aromatherapy puzzles without drawing plans.

Placing the Master Builder on the path does indeed produce the scaffold, and now work is continuing apace on moving the statue.

(Oh, by saying the same experience I mean that the chalkboard shows plans for the bath AND the statue.)