I would hold court!!
Gather the persons that have permission to access the farm and set up ground rules. Let them know that theft is lazy and illegal(and is also grounds for a severe whoopin')!!!
You could organize a sign-in sheet that must be signed before anyone enters the property with dates, times, and stands used.
A simple mass email would suffice. Chances are these guys will go for it, because it will also prevent 3-4 guys all showing up to hunt the same stand!!!
You probably won't see that cam again(until you put the fear of God into them)!!!
Good luck