I just had my first significant loss as a result of having children (I mean, other than uninterrupted sleep, free time, disposable income, and sanity). Chloë dropped my Christmas ornament from 1994--a small real snow globe--on her tiger "piano" and broke it. "It didn't break the first time," she said, "but it did the second time." I asked her why she dropped it twice, but didn't get an answer. She did alert me to the incident by saying "Mama, I'm very sorry," and repeating it until I told her it was okay.
She was upset that it had happened, and more upset that in the course of cleaning up the glass and sparkles I accidentally sucked up one of Maia's socks into the vacuum. I told her I was a little sad the globe was broken, but it wasn't a big deal, and neither were the socks. It really isn't a big deal, but it was my 1994 Christmas ornament and I remember going to get it. We've lost other property to her or Maia, but this is the first thing I can think of that was irreplaceable.