I'll never forget when M was in Kindergarten and starting checking out library books for the first time! It was such a task to remember to bring that library book back every other day in order to check out a new one. I reminded her the first three times to make sure it was in her backpack the night before, but as every parent does that first year, I forgot once. M discovered it 5 minutes after walking across the street to our school (yes we live that close), she was still in my classroom before school had started when she discovered it and begged me to run home and get it for her. I said no gently, that the library book must be her responsibility. She cried, I was heartbroken, I toyed with the idea of getting it at lunch and it bothered me all day. Every time I saw her in the hallway she gave me a puppy dog sad face. It was one of the hardest things I ever did BUT fast forward to third grade and she RARELY forgets her library book and if she does, she handles it beautifully and goes on with her life knowing there will be another check out soon.
In my classroom I also send home take home folders and book bags for THAT reason. It is the students' job to make sure those go home and come back every day. I will not accept that it is mom, dad, or Billy's fault. I do not make a big deal out of a lost folder or bag, but they do, and most of the time they come back with it eventually. :)