I am assuming you are talking about a trail cam? That just sucks, I get so tired of people out for a free ride. Friends of mine have tried two different approaches that have worked.
1) They set up a cheap trail cam where they were having problems. They then placed a good infrared camera up in a tree where it was very hard to see to get pics of the thieves.
2) They bought one of the newer cameras that allows the pics to be downloaded to your phone. They haven't had that one stolen yet, but the thought is that they might be able to get pics of the thieves even after its stolen.
Just sucks that honest people once again have to pay more to enjoy their pastime because of dirtbags.