My dad was a park officer/ranger. He said any time you take personal property you must give a receipt and then write a report and register the item in the evidence room. He said to go ask for a receipt and the possibility of getting you property back. If the item is not in the evedence lock up you can take up the issue with the parks management. State the day, area, and time you were stopped and they should know which ranger it was that stopped you. If there is no paper work or the knife is not in evedence then the officer stole you knife and there should be disciplinary action against that ranger for stealing evedence and personal property. Good luck.