Does this Sign Hold Up in a Court of Law?

I am a pissed off DJ. I Was talking on the radio today about all the money under my floor mats in my car was taken (or should I say STOLEN) from a local car wash.

Now I can't prove it 100% that they are responsible, but they are the only car wash that I go to that I had vacuum the interior since I have gotten the car.

I don't understand how a business is let off the hook by posting a stupid sign in their shop or office. It's in MY car. It's NOT yours. You take something out of my car, you ARE STEALING IT!!! Simple right? Makes me so ANGRY!!!

Are businesses ACTUALLY responsible? Do the signs that they post in their office hold any weight in a court of  law? Or is it all B.S?

Comment below please. Let me know what you think of this