Thou shall not do your own septic system? I am surprised that the deputy did not sitck with the little lady as she did her inspection, since he didn’t stop her from going on the property. If Indiana law does not grant her the authority to inspect without a warrant, then her evidence would be useless. If it does, then no law was broken. Counterclaim and sue.
I would seriously doubt that an inspector can just walk onto your property.
I know here in St Petersburg, FL they cannot. If you fence your property they are not even allowed to touch your fence. They can look over etc. but they are not allowed to simply walk onto your property.