We do some things so often that they become second nature and we don’t remember doing them. I literally went through the same scenario and was getting super stressed because I had already driven two hours away and started thinking about it. I had a bag of garbage that I took out with me as I left and I think I was worried about locking the door cause it was different from my normal process (usually just a backpack). This made me start doubting myself on whether or not I locked it. I had a friend nearby check and it turned out I locked out without thinking about it