As scroca says, they probably forgot you were there. I never rely on a motorist's memory. I also never rely on a motorist to do the right thing. I force the issue to my favor.

I use lane position to counter this sort of thing. At a light I never let a car be next to me. I drift left and put myself in the lane either ahead of them or behind them, never next to them. If someone tries to pull alongside, I pull further left and forward.

If there is a shoulder instead of a bike lane, I ignore the shoulder and move left into the lane.

This means I'm either in their direct forward vision, or safely behind them. Usually I'm in between two, since this lane position means I rarely filter, because that puts me back next to a car, precisely where I don't want to be.

When the light turns green, I stay slightly left until I pass the crosswalk, then move right (if there is space) allowing the car behind me to pass.

I can't speak for California, but in New York State, this is part of the reason why bike lanes disappear at intersections. Unless there is room for the right-turn lane to completely be to the right of the bike lane, then the bike lane disappears in order to make bikes and cars merge into the same lane, one behind the other.

This also explains why at intersections with "bike boxes", they're placed to let cyclists move from beside the cars to in front of them.