Why did you leave the antenna on the car in the first place? It's a pain to take off and put back on, but you would still have your antenna. I take my radio face plate and antennas in when not in use. My radio and amp is in my trunk so it would be hard to steal.
But it still COULD be stolen. If you REALLY want to protect from theft, you need to install the gear every morning when you get in the car, and then remove it all when you get home in the evening. OR, you could sit on your roof all night with a gun and a thermos of coffee, and PROTECT your gear.
Oh, you're thinking that wasn't very helpful? Criticizing someone's message with irrelevant complaints that the original poster didn't do what YOU think he should have done? Sorry. I can see where you'd find that annoying.