1. Create public segment of said trail
2. See who pops up on the leaderboard
3. Comment on their ride asking them politely to set the ride to private
4. Delete segment
I've been doing this once in awhile, just to make sure a trail I had built wasn't showing up online.
I just did this again now and I was a bit surprised a very prominent person in the mountain bike community had a strava'd my trail.