Your message is not clear!
1. IF you picked something up from the NPS property, turn it in, it is federal crime to remove items from federal property, my recollection is 25,000 dollar fine, plus prison time. The NPS does not look kindly on this type of activity. Even if it was historic or modern!!
2. IF the item was picked up off site, and there may have been a living history or similar activity, there is a 6th Louisiana Living History Organization in Pennsylvania.