We're both making assumptions here, that is literally the point of this subreddit.

My argument is that YOUR assumption (that her foster parents murdered her and got away with it) is less likely than MY assumption (that she was picked up by someone and something bad happened to her/she ran away).

I never gave any reason for you to ASSUME I believe foster parents are saints. This is my last paragraph for you to read again: Anyway, there isn't much info about the case, so it's impossible to say either way. I just think it's way more likely that Lindsey ended up being picked up by the wrong person, especially on a day that attracts people from out of town. There isn't anything substantial that points to the foster parents being suspicious. Yeah, foster parents can be shit, but they're generally not murderers. I'd think if they could have possibly murdered a teenage girl in their foster home the RCMP would know about it.

The only thing I would make more clear is the last sentence, which you seem to be struggling with. So yes, you're right that it is possible they could have murdered her and it is possible the RCMP wouldn't know about it and it is possible that aliens are reading this entire conversation and laughing at us. But I want to go by what is more likely, and so does the mother and the foster parents and the RCMP and the people in town and the people in this thread. And what is more likely is that she ran off, like she ran off many times before, except this time she didn't come back.