Why wasn't Theresa discovered sooner?

Photo 1: Compton Station Road (looking toward Gagnon farm)

Photo 2: View from Gagnon farm looking toward bog/bridge.

Photo 3: Side view from road showing Gagnon farm behind clump of trees on left and the bog treeline next to the bridge on the right.

Photo 4: Where Theresa was finally discovered by muskrat trapper in April 1979. (34m from bridge)