On an idea I had, what can I do or should I do if I thought the county was using something I thought of?

It is possible that two people can think of the same idea at the same time. The idea itself is not protected by law. However, the expression of the idea, be it an invention, a story or song, or any thing else suitably original, will be protected in many but not all cases. To take action against the county, you will need to show that you created the original expression of the idea, that your expresion was protected by law from infringement, that the county had the opportunity to learn about your expression, that the county copied or used some or all of your expression without your permission, and that you suffered a loss as a result of the county's action.

Regret that it is too late to protect your invention.

Unless you can prove that the county took your idea - there is little that you can do. Often two people will develop similar ideas at the same time - especially if directed to a well-known problem or issue. Sometimes the solution is obvious - and multiple parties come up with the same solution.

Unfortunately if you don't have any rights to the invention then you are out of luck. Keep in mind you don't have rights nor can you gain rights to an idea. You must have an invention or what we call an embodiment to be able to patent it. For example it is an idea to have a touch screen computer, but it is patentable when you can write a specification that tells someone who knows computers how to build and use such a device, Now if your idea was fully developed and you showed your plans to the county employee who is using your "idea" you could possibly keep him from getting a patent on it as it is not his idea, but you cant go back in time and file a patent to gain any rights in your "idea" now. That ship has sailed.