Those thieves were pretty determined and managed to get around most of your ingenious measures. Did your neighbors have trouble, and did any of the locals suggest who the thieves might be?
That area of the locality has always had theft issues which is why we just bought other property and moved everything. We recently suspected our closest neighbor as the thief, he's in his 40's, is an alcoholic, does not work and is a known thief to fund his life.