This is slightly different than you described, however worth keeping in mind. On my Georgetown XL 334QS, when the door is locked from the inside, it can still be opened from the inside in an emergency without moving the selector to the unlock position. If the door is opened in this manner and a person exits the MH, then closes the door, the door is locked from the outside. If you do this and do not have a set of keys with you, good luck getting back into the MH.
Unlike your scenario I have always been able to unlock the door from the outside with keys.
John & Gloria Hunsaker FROG Member CA-0030-988
2014 Georgetown XL 334QS (class A with 4 slides)
2013 Smart Car TOAD
Blue Ox Aventa LX tow bar, base plates, diode kit
SMI Stay-IN-Play Duo auxiliary braking system
25' Off shore blue water fishing boat