Are you talking about this photo? 
Those are they. Whilst the clarity leaves something to be desired it’s possible to knock up a couple of sectional plans and elevations of what can be seen, then work out what you should see if it works how you seem to think it does.
For example if the knob operates anything in the lock you would see the linkage or evidence of it. Nothing like that can be seen.
The knob is a single dummy having neither latching nor locking function.
The door appears to pull closed against a shoulder or weather strip. That gives a clue about using the credit card dodge.
The lock assembly shown clearly has a dead bolt in the upper part of the lock with a latch bolt in the lower. The latch bolt tongue that can be seen is a conventional fabrication where the wedge is welded or brazed to the flat plate. ie the flat plate is NOT a plunger.
The latch bolt is likely fitted with a spring loaded manual actuator to pull it clear and hold it clear, by rotating it through 90 degrees,such that you do not lock yourself out while you are dicking about running in and out with the groceries.
There is nothing clever and nothing unusual about any of it; just basic security measures installed in an “L Cheapo” holiday apartment.
Possible attitudes are:
Latch bolt closed and dead bolt open; this requires a key to gain access from outside and manual operation of spring loaded actuator to allow egress.
Dead bolt closed and latch bolt open*; this requires a key for access or egress.
Dead bolt closed and latch bolt closed this requires key for access or egress.
• Pure speculation on my part that this can be done.
