A while back, before I knew the game very well, I obtained 3 pictures from my villagers. (not by blanca) Spork, Merengue and Willow were all in my town at once and I loved them dearly. My main room was dedicated to their pictures. However, my friend (was very new to the game) and I played together, and he got my game instead of a blank copy that my brother wasn't using. I'm guessing he looked up how to change the date on a ds, or animal crossing, because when I played my copy, I noticed that weeds were everywhere, I opened it, and I hit my town map. Willow had left and Merengue was in boxes. I tried to turn back time a day (don't do this) and ended up moving her out. While I did have Spork, I also got Cherry, whom I would later despise. I didn't like her personality, nor that she moved in front of my accidental blue violets. Which took me forever to get. Not to mention, I had never experienced Halloween before in acnl, and they RUINED my clothes. (Didn't know about catalogging) I reset my game because I got so mad and upset in so little time. I couldn't stay mad at my friend though
TL;DR: Keep your cartridge with you at all times