Spork3245

Remote Start has a timer of which you can set in the info display. The available times are 5 minutes, 10 minutes or 15 minutes (15 minutes being the default setting).

I'm unaware of the 2015s, but the 2016s are supposed to autolock after 45 seconds.

AK_Kayaker

HMMMMMMMM according to the 2016 owners manual, they have an auto relock lock feature, so if you unlock but don't open the door within 45 seconds, yes it will relock, but that is the only thing about such a feature I was able to find.
Really people is it so freaking hard to push the damned button on the fob to lock the damn doors, I guess cause I grew up with cars that you had to actually push the lock button on each door, and some required you to hold the latch down while closing to make it lock, and holy crap if you went into the store and thought did we lock the car, you had to go all the way back, and manually lock them.

Spork3245

My first Mustang had two keys: one key for the doors, one for the ignition. No fob.

Anyway, the autolock on the 2016s won't engage if anything is open; doors or trunk. My guess would be the trunk was left open.
Personally, I don't trust the autolock and either tap the lock sensor on the door handle or hit the button on the fob. It's also unlikely the trunk button was hit on the fob accidentally considering it needs to be pushed twice in a 2-3 second period to pop the trunk.

AK_Kayaker

As I stated please read the 2016 owners manual, as it says nothing about an auto lock feature, other than the relock one I mentioned.

Spork3245

To exit the Mustang the door must unlock...

Spork3245

Are you attempting to say the only way to unlock the door is via the fob and thus that would be the only way the autolock would engage? Because if that's what you're saying, you're incorrect.

AK_Kayaker

There is no autolock feature............period.
There is a feature that if you use the fob to unlock the car, then do not open the door within 45 seconds, it will automatically relock, as per the 2016 owners manual.

audioAl

I've had a fob accident once in my 2014. Walked out of my job and the trunk was a jar.

66to2016

I lock my car every time I walk away from it. Even if I plan on going back out right away to the store. We have auto-flush toilets at work...now when they fail people are too stupid/lazy to flush them

CaptainX

I've never tested it, but when I get out of my car, and walk away, the doors make a click (which I assume is locking them, as the sound is identical) though hitting the lock button makes this sound again, and hitting the lock button twice beeps the horn to signify the alarm is set. Which brings on another point, as when I get out of the car it asks what alarm features I would like to employ, I usually leave it at all alarms, or whatever (the other option is proximity sensors) so I dunno if that's saying it's gonna automatically engage the alarm for me. I have had one instance where I got in my car in the morning and the "Truck ajar" notice was on the dash display, sure enough my trunk was popped. I don't think I hit the button when I was getting out or into the car, so I'm not sure when it was popped, or how. I know when I put the car in park and turned it off, the trunk was shut.

It's probably people hitting the key fob accidentally, but there's a possibility of a defect in the trunk lock mechanism that is causing this to happen to people.

EDIT: And no, the click I am referring to is not the window locking in place