Second key causes alarm

[pzh20]

I did a stupid thing today, opened the drivers door and tossed my keys onto the seat. Opened the rear passenger door and rear hatch door of my 2017 GLE.
Closed the drivers door, closed the rear door, put my dog in the boot. Closed that door, then noticed the car was locked!!!

Firstly, does the central locking lock the doors automatically?

Anyway 50 quid on a cab home and back to get the spare key, when I tried to unlock the car with the key fob, the alarm went off! I used the actual key to open the car, and use the jailed key to turn off the alarm.

Is this by design or a fault?
Many thanks

 

[Smart320]

How’s the dog ?

 

[fourwheels]

I did a similar thing a few years back. Chucked my coat, key in the pocket, on to the back seat. Shut the door and it locked. Impossible! But obviously found the one location that it would lock but wouldn’t unlock.
Wife had to drive 20 mile round trip with spare key.
Only afterwards I discovered that if you have the Mercedes Me app on your phone with the appropriate add-on you can use your phone to unlock the car.
Worth checking out Me.