if it's in a room with a computer, get a webcam. at my last job, we had someone use things around the office without putting it back where it was suposed to be so we used a webcam pointed at the specific section. Then we got a software that detects pixel change in the video so if the camera changed enough, it would start recording for a set number of mins or secs.
Once it's recorded, you have it on your computer. plus, webcams are now super cheap to buy and the quality is allright. some are even wireless and small enough to hide in anything.
motion detection is what you should be looking for if you go the webcam method.
like this:
http://ask-leo.com/can_i_use_my_webc...y_monitor.html