locking gas cap

I called the chevy dealership about a locking gas cap and they told me that they don't have one but that you can't syphon gas out because of a ball that pops up in the tank neck when you stick something down the tube. Is that correct?

If they say so why doubt them, most vehicles have this to prevent spillage in a roll over. Try and get a syphon tube down into the tank.

I called the chevy dealership about a locking gas cap and they told me that they don't have one but that you can't syphon gas out because of a ball that pops up in the tank neck when you stick something down the tube. Is that correct?
Locking gas cap might not be a good idea. I would rather them siphon gas out of my tank than punch a hole in it.