Whoever built that shelter should spend a rainy night in it. I think they would learn a great deal very quickly.

To address the signalling question:

I think it takes something big, high, and unnatural in colour/shape to attract attention from a mile away or more.

E.g., limb up two trees as high as you can reach, and ...

- tie a space blanket across the two, so there's a big reflective rectangle

- tie flagging tape across in strips that are close together so it makes a big orange square (or a big fat X)

- wrap an orange garbage bag around the trunk of each tree.

A small signal fire or a flashing red bike light would help these items to stand out at night.

My 2¢.