Hi Eileen, and welcome to the forums.
I have been selling our eggs for oooh, 8 years now. I have had one person take eggs and not paid, and a couple of people have put a foreign coin in the box.
But after a lady down our lane who sells veg had someone just take stuff from her front gate without paying, My eggs are not at the gate, they are sitting in a plastic box outside the front door and I used to have a noticeboard outside saying we had our own fresh eggs.
Now, I've taken the board away because we couldn't keep up with the demand, but our regulars just look, and if they see eggs they buy, if not they wait til we have some!
It is a shame you have had those eggs taken like that. After all, chicken feed isn't cheap these days!
Some people have a notice outside, but make customers knock for their eggs, but that is difficult if you aren't at home all day.