I arrive in LA from Toronto at one of the domestic terminals (terminal 4), get off, walk to the international terminal (terminal 3) to catch my flight to Australia, go through security, and wonder why my flight isn’t listed on any of the monitors.
Finally, I realize. It’s because it doesn’t leave from the international terminal.
No, bizarrely, it leaves from the domestic part of terminal 4, about 100 meters from where I got off my Toronto flight.
So I go out past security, walk back to terminal 4, and go through security again, to get to the gate.
Fun.
This story happened about 6 months ago. I just repeated it about 18 hours ago, with “Toronto” replaced by “Boston”. Fortunately, I remembered before getting through security in the international terminal.