A year or two back, I locked myself out of my home. I went outside to get mail and out of habit, I locked the knob from inside, then closed the door behind me without carrying my key.
When I called a locksmith, he used a thin metal card into the latch area instead of futzing with the cylinder. The latch has a small side pin that rests on the jamb plate so the latch can't be pushed in with the door closed.
If the card job opened the door, does it mean my jamb plate is out of alignment or did his technique somehow bypass the interlock?