When old wounds bleed afresh

It's 436 in the morning, and I can't sleep. Something's bothering me, and I've got to write. Beats tossing and turning in bed.
 
The thing is, I've just checked my newly bought DVDs for defects, and one of them was a Faye Wong MTV collection. Most of my friends know I somewhat like her, though I've never been to one of her concerts. Anyhow, I watched some of her MTVs and decided to go to bed. Then something stirred in my head. I had remembered that I bought 2 VCDs of her MTVs a long time ago, way back in secondary school. What happened was (and I'm pretty sure of this memory) that my sister( the older of two younger sisters) brought it to her friend's place, lent it to her, and when they returned, one of them had no disc in it. The worst thing was, despite repeatedly reminding her, it never came back. She even said something along the lines of 'it wasn't nice anyway'. I was very upset, naturally, but I can't remember how I dealt with it. The VCD is now unavailable, which makes me more upset because it means I can never go buy a new one. This memory haunts me to this day, and it just popped up again. I just went to the disc drawer to check, hoping I was wrong and the VCD was somewhere. But it wasn't in the sleeve. There were songs in it I liked. Once again, I was disheartened, and disappointed that my sister had no regard for my property. Which is odd because it was a long time ago when this happened.
 
This thing that happened a long time ago should have been forgotten. I'm not really angry at my sister, but she can be very careless, and strangely manipulative sometimes. I don't know why I still feel that residual bitterness.  Recently she took my Tianlongbabu to her boyfriend's place, it came back with one disc missing! Luckily I checked and reminded her and it turned up. It's on loan again, but I'm pretty confident it will come back complete. So, no bad feelings, not really. I love both my sisters, and I don't really mind if they occasionally get on my nerves. But I have no idea what went on in my mind, and why it chose to preserve such an awful piece of memory. Worst still, I have never thrown the empty cover away. I wonder why.