World's Loneliest Fieldtrip

First, most of the people in the class go home, knowing they don't need the fieldtrip. Next, there are 5 people left, including you. Three of them leave because they have to meet someone. And finally, the last one leaves because they have an appointment of some kind. This leaves you completely alone with the instructor. The resulting fieldtrip is so nostalgic that you can't help but use the bathroom of whatever facility the trip takes at, because your lunch is telling you it wants to move on after seeing the amount of progress you're making.

Key sign that one is about to start: Everyone in the class is staring at you when you say you'll go and you're the only person raising your hand. Prepare to be swamped by loneliness and nostalgia.

If you use this term, your trip might not be the record holder for the loneliest fieldtrip, but it might feel like it.
There are various factors that play in like isolation, space and nostalgia. So depending on the conditions, you may or may not be the record holder.

You're on a phone call with a friend:

You: Hello?
Friend: Hello. What is it.
You: I'm alone on the fieldtrip.
Friend: I told you know one would go.
You: This feels like the world's loneliest fieldtrip.