Thank you for the ideas. I thought about this "lock" for yet unseen events but it wouldn't really fit the game in my opinion. Anon is supposed to have a feeling of unimportance and things just happening around him and I don't really like the idea of a event basically waiting for him to show up.
If finding a scene is just too tedious, there's always the gallery hints to figure out where to go.
Eventually there will also be the LFG board in every town to direct Luna towards a specific NPC. I like those solutions a lot more.