If all the train tickets you bought in the past were purchased online at 12306, you can log on to your website at 12306 to inquire about the tickets booked at 12306. You can check the ticket information within 30 days from the booking date, and do not provide other purchase methods for the time being.
If you check it at the train station counter, the staff at the train station can check it, because it's all in real-name registration system now, and the train tickets you bought have a history. However, the staff of the railway station should not help you check, and the participation of non-public security organs may not necessarily help you check. Besides, I'm busy now, and I don't have time to help you check this.
When conducting investigation, the public security organ may look for relevant records from the system of the railway department, and other organizations and individuals have no right to look for them.