The reason people own copyright to mechanical cameras and the like is because intent matters in copyright law. Believe it or not, copyright does NOT automatically goes to the person who presses the button - it goes to the person who sets up the shot. (These cases up not fairly often, so there's plenty of legal precedent here). If you ask a bystander to stand somewhere with your camera and take a picture of you and your wife posing, there's good legal argument that you still own the rights to the photograph. (Mind you, more often this leads to shared copyright than exclusive copyright, since the person snapping the picture usually ends up having some input into the result and thus an arguable claim to being a creator, but that's not really relevant)
So if the man had *given* the monkey the camera, or set up a mechanical camera, it definitely would fall under copyright as being his, since he had intentionally created the shot (even if he wouldn't have been completely aware of the result).
However, if the monkey stole the camera, it's unlikely the man would be legally classified as being involved in the creation of the shot - merely owning the hardware isn't sufficient. And he probably shouldn't be, either. It wasn't a creative act, and while he might win a case if he find a sympathetic court or one that's already been bought off by the IP lobby, I think it's pretty clear that he shouldn't be able to win under the current IP management framework, since you can't claim copyright over found or natural objects, and it's pretty obvious the pictures should be classified as such in this situation.