Land mines. They're Grrrrreat!
In the beginning I'd be pissed. I'd probably not change anything, and leave my stash right where they took it from. Except this time I'd take a lesson from the bank and put an exploding satchel in one of the bags. Except instead of blue dye I'd use ammonia nitrite and a few other select household compounds.
I'd dare them to come back and try it again. Then all I'd need to do is find the man with 2 fingers and scorched eyebrows.
I also suggest the motion lights. Dogs are probably the worst security system ever invented. Unless they are VERY well trained a dog no matter how large can generally be circumvented with a pack of hot dogs or some lunch meat.
In order to keep his home safe though I think an alarm system is the only option. Every American in my opinion should exercise their right to use firearms to defend their homes, so get a gun, and then go practice with it. If everyone here seems pissy about inexperienced shooters then go get yourself some experience too.
Sharks, Laser beams, trap doors, ill tempered sea bass. All very good options.
Uh...this isn't hollywood, and throwing a steak over the fence is not enough to keep a trained dog from attacking an intruder. Some of you guys must live in fantasy worlds, must be nice.