In this sentence, the person that said it, is explaining how when they saw the toy, it brought them memories of a time when they were lost in the rain forest. It could be that while they were lost, they had that toy with them. It’s similar to how someone can look at a picture they took five years ago on vacation and remember something about that moment when they took the photo. For this person, looking at the toy brought back a memory associated with that toy. You can use this whenever you have a memory associated with something. This could be something that’s an object, a smell, a noise, picture etc. A good term for this is called “Nostalgia” which is experiencing a memory due to some stimulus of a person, place, thing, smell, sound etc. A good way to use this would be if you saw a toy from your child, it could stimulate you to experience a memory. I hope this helped!

When you say that something "brings back fond memories" of a certain situation, it means that you always remember that memory when you see that particular object. In the context of this sentence, you fondly remember being in the forest, each time you look at the topic.