This has happened to me a number of times as I’m still figuring out the roads. All of a sudden I’ll see one lane backed up and the one that I’m in is suddenly empty. Then as I pass all the cars I slowly realize that my lane is something like a “Right Turn Only” lane and that’s when I become the dick who went up as far as they could and then just cut in at the end.
I’m sorry drivers of Los Angeles, I’ll make it up to you by signaling at every single turn even when there’s clearly no one around. Actually I do that anyway because I find the feel of the turn signal switch very satisfying.