I am a little puzzled as to why Mr. Anthony kept the wheel chocks (wedge) in the Pontiac. As best we can determine that car was mostly driven by Casey and if one has car problems and needs a tool, chock (whatever) you want it at the home where you would be working on one of the vehichles, no? Why in the car of a young woman who seems to like to be off and about a good bit?
They have 3 sheds and their garage was very organized and their yard, home etc looks much the same. If Mr Anthony is one prone to work on the cars rather than take them to a shop, the chocks would be kept at the home in my idea if logic. I certainly don't think Casey seems the sort to work on her own car, if so she obviously needs a few gaskets, as that Pontiac appears to leak a good bit (oil stains on driveway).
My point...it seems to me Mr Anthony knew or strongly suspected Casey had taken the gas cans and he wanted to look in her trunk. That was just his excuse to look....but imo he had a reason be it gas cans or whatever, he wanted to see inside that trunk.