I was interested in "how" they were stealing the traps (which I never did find out.
From my years of experience of winter camping ( and dealing with mice stealing food and socks from my floorless tipi), I can attest to the strength and survival drive of mice. Your trap's disappearance was probably caused by mice that were caught( but not killed....like only a foot caught), dragging them off to a safe location. Or else, you also have an infestation of the dreaded "giant New York cockroach"..... in that case...... move. :-)