You find them in fixed locations. I don't think any of them are missable, but you just gotta keep getting further and getting more of the permanent progression items.When do you start seeing more weapons?
It's related to the story. There's some kind of specific triggers to seeing more scenes happen, but that's all it is. If you tend to make rapid enough progress without dying too often, it's a good idea to explore enough of the 1st biome every run to see if it's open.Also, is there a reason I can't go back in the house after the first time? I still have the key but the game says it's inaccessible when I walk up to the door.