Samuel the escape artist

I turned samuel's doorknob around to his room, so that I could lock it from the outside, and I wouldn't have to keep dealing with him always coming out, whenever I put him in time-out or down for a nap, or bedtime. The doorknobs we have are the kind that can be unlocked from the outside with a penny, or knife or a long sharp fingernail (which I use). As soon as I turned Samuel's doorknob around, he began finding things in his room he could use to unlock it with. Since he would be so proud of himself for unlocking the door he would show me how he did it, and I would confiscate the object, so he couldn't do it again. I have pretty much emptied his room, of any object that could be used to unlock the door. Last night I had to put him in time-out, so I took him into his room and then locked the door and set the timer for 3 minutes. He was quiet, now when Samuel is in time-out he does 1 of 2 things, he either screams and cries until his time-out is over or he is quiet. When he is quiet he is thinking, and figuring out a way to escape. About 30 seconds into his time-out I noticed that the vaccum cord was moving.(the vacuum was in samuel's room, but the cord was plugged in in the hallway.) I went to investigate and discovered that Samuel was slowing pulling the vacuum cord into his room via under the doorway. I thought that the actual plug would get stuck and not fit under his door, but when it did get stuck, he managed to pull hard and get it all the way into his room. He then proceeded to pick the lock with the prongs from the vacuum plug, and opened up the door. He came out smiling and brought me the vacuum plug, and said "mom, I got out with this!" I couldn't believe that he had figured out that he could use that to unlock his door, but it was nice that he is still so innocent that he will tell me everything he does.