I've been to Israel twice, including to Yad Vashem. They have a section on non-Jewish victims as well. It's obviously not the focus but as a gay man myself, I remember seeing the pink triangle there. Granted I was 19 when I went so not a kid and I already knew what it was and what to look for. Perhaps a child would not yet be taught about the triangle and so wouldnt even have noticed. Certainly when I was 12 I was not taught this. But that was almost 30 years ago. Perhaps these days they do teach that.