Cat mysteries - a double bill

We present two mysteries for your reading pleasure. The first solved, but remains an open case in the C-files. Read on, dear sleuths, and see if you can make heads or tails of the cat mysteries.
Our first tale takes place during a visit of two couch surfers from Australia. They had been with us for a day and a half already, so they knew our routine with the cats, and to watch for them as you entered and left the house. Toulouse is both sneaky and fast, however, and we weren't surprised to find him missing when we went to bed. We searched the inside of the house, top to bottom, with no luck. Despite our guests claims that they were careful, we assumed that Toulouse had bested yet another human in his never ending game. Where the mystery begins, is when we tried to get him back in. These days, when Toulouse does escape, he usually wonders for 45 minutes, and then comes back when we shake the treats and scratch him while he eats some grass outside of the house. This night was different. 3 hours of combing the streets and a cramp in my hand from shaking the treats gave no results. We ended up opening the old cat door and restricting Chupa to the top floor, hoping Toulouse would come back when he was ready.
Now I am a sound sleeper, but I was woken in the middle of the night by Anna who was convinced she heard scratching near the fireplace. Our bedroom is in the basement next to the fireplace, and Toulouse has seen us letting trapped birds out of the fireplace before, so we thought he may have climbed up looking for another. No luck. It was empty, and the sounds had stopped. Early the next morning, I wake up again, to the sounds of Anna meowing at our bedroom wall. My curiosity exceeded my desire for sleep so I watched until I too heard a meow in response. It took about 15 more minutes to solve the mystery. We double checked the fireplace, and searched the openings to the air vents, before we realized that you could access a crawl space between ours and our neighbors house from the furnace room. This crawl space is very narrow and is a maze of pipes, so any cat that managed to work there way in there, would be out of luck if the lights were turned out in mid adventure. (cats cn see in very low light, but pitch black - I assume). So a few minutes of shining a flash light at the escape route, and gentle coaxing brought the escapade to a close.
Our second mystery, is stranger still. Toulouse has not only mastered the at of escape (front door, and back yard fence), but he has also mastered pulling the heart strings. Anna is convinced that keeping him inside is slightly short of torture, so we will occasionally take him for a walk on leash (he has mixed feelings on this one), or Anna will let him out for a quick stroll once it is late enough and there are no cars or people around. He has learned to accept this compromise, and comes back within 30-40 minutes. Last night we did the same, and kept to our routine of letting Chupa in the back yard, while propping the front door open for Toulouse. No surprises, as Anna brought Toulouse back in and brought Chupa from the back yard. On my way to bed, even I remember seeing Chupa playing with a cord. The mystery begins the next morning, when I wake up and see the front door propped open. I wake up Anna, who confirms what I remember - the cats had been brought back in. So how did they escape? was the door not closed properly? had someone cam into the house during the night? (we don't always lock the door - this is Canada after all) :) I get dressed to go searching for Toulouse, when see him walking past my feet. All right, one cat found, he must have come back in when he got bored, but Chupa is not used to wondering, and expected he would be tougher to catch. Now here is where it gets really strange. I look in the back yard, and see Chupa sitting here waiting to get in. Now the back yard is enclosed, which is why we let him roam there when the front door is open. Toulouse can scale the back fence, but not Chupa. We didn't forget to let him back in, but did we sleep-walk and let them back out again? It so closely fits our pattern of letting the cats out, that we can't think of any other explanation? any thoughts from our sleuthy friends?