Find my iPhone

I unfortunately lost my AirPods and i was using the “find my iPhone app” to track them and it said they were on train tracks because the last place they were on was a train and I was waiting for someone to find them, but I checked this morning and they were still there and then I checked 2 minutes ago and they’ve completely disappeared and there not even a device that it gives me an option to find.

What do I do?