Luck, Love or Good Behaviour?

Every day as I arrive home from work, I look for three little canine noses squeezing our from beneath the garage door as it opens. Today I got the fright of my life as two furry bodies hurtled towards my car before I had even hit the automatic garage door opener. They had come from the back of the house, outside the fenced section. If the fact that they were out did not freak me out enough, that there were only two sent my heart in to rapid palpitations. It's amazing the scenarios that can run through your mind in a short space of time. Fortunately a sharp bark from behind the garage door allayed the fears that I had lost one... but questions remained, and still do.
I think I have backtracked to figure the escape route. My own fault, coupled by a dodgy gate lock, which I have had fixed many times. I guess that it did not close properly after I had hung out some washing this morning. Because the gate sticks at the bottom, it looks and feels like it has closed, but as these re-enactment pics show and as is often the case when I'm at the washing line, persistent little noses can coax the gate open when it's not fully snibbed. From the inside, that is. The gate had closed again, and I imagine they could not get back in to the section, even if they had wanted to. My forensic examination saw scratch marks at the bottom of the gate from the outside, so I figure they have tried.
So how they got out is probably ascertained. However the questions that remain unanswered include...
How long were they out?
Did they roam and then return?
Who lead who astray?
How come one stayed inside?
Was it love, luck or good behaviour that kept them safe?
and a question I prefer to remain unanswered anyway... What if???

Oh, a couple of questions for any readers who know my canine kids...
Who do your suspect was the initiator of the escape plan?
And which one stayed inside?