I've had numerous paranormal experiences in Gettysburg. This is one of the scariest.
I was near the Rose Farm, off of Confederate Avenue, looking for the location of a New York Artillery Battalion. It was August, hot, muggy; just typical summer weather... It wasn't super windy, but there was a nice breeze blowing. As I walked through the trees, I could hear leaves rustling, birds singing; just normal summer sounds. I followed a narrow path leading to the cannon site, which is about 150 feet into the woods. At first, I didn't notice anything strange, but suddenly I realized there was absolutely no sound AT ALL. Even though I could see the trees moving in the breeze, it was dead silent. And COLD, like I had stepped into a freezer. I stopped, unsure if I should keep going or turn around and leave.
I should point out here that even though I've had many paranormal experiences in my life, I don't scare easily, but what happened next sent me running like a scared rabbit.
I saw a flicker of movement out of the corner of my eye, but when I turned to look, there was nothing there. At least nothing I could SEE. I heard the sound of a match being struck, smelled tobacco, and a voice said clear as day (and very close to my ear), "You don't belong here. Get out!" At that moment, the silence broke with the sound of a cannon firing and I took off like the Devil himself was chasing me. I sat in my car, shaking, trying to gather my wits and process what had happened. Once I calmed down, I drove back to town and talked to one of the Park Rangers. I don't recall the gentleman's name, but he told me I wasn't the first person to have that experience.
A couple years later, in 2008, I went back to the site with a friend. This time, we both experienced what I had 2 years before. We have been to Gettysburg several times since that day, but neither of us went anywhere near the Rose Farm again.
Did you keep the hand-carved pipe you found in your car as a memento? Such phenomena are particularly unusual, especially as the voice you heard was telling you to leave in what seems to have been an unfriendly manner. I wonder if your reaction caused the entity some regret, hence the 'gift' left in your car.
Best,
Biblio.