...So, on June 16, KC returned to the house after GA had left for work and most likely used her own key to gain entry to the house via the garage entrance door (the A's have stated that this is the normal/usual way they enter the house). She most probably also left her car on the driveway as she was not supposed to be there (told GA she was off to 'work') and so would be leaving again at some point...
...according to CA/GA, the gate was not only unfastened, but was left open. I think this is because whoever used the gate on that occasion was a) carrying something using both hands/arms, and b) in a hurry to get that 'load' into the car and away.
So, if Caylee died inside the house, I would expect KC to have carried her straight out through either the main front door, main garage door or side garage entrance door and to the car there would be no reason to exit through the side yard gate, thus leaving herself unable to refasten it. Conversely, if she died in the back yard, would it make sense for KC to then carry her in through the house and out to the car via any of the exits as above, when the shortest, quickest route was through the side gate? This leads me to believe that Caylee did indeed die in the back yard. I think just after deciding to flee, KC may have gone into the house to get a covering and bag to wrap the body with and to collect her things. She probably then went out the side garage door, put her things into the car (possibly also anything else that she needed to take away from the 'scene'), and then opened the trunk. I think she then returned to the house, locking the side garage door from the inside, and then went out to wrap Caylee's body in the back yard. She then carried her through the side gate, into the trunk and away as fast as possible no time to close the gate, and impossible now to refasten it.
Finally, if June 16 was indeed the day that the gate was left open, it was also the day that the pool ladder was left in place. Why was this? I'll leave that for others to theorise on, but I'm sure by now it's clear what I think the answer is!