Well, I think this is a messy personal situation, and your emotions are understandable. These were your things that you felt forced to leave behind. That’s upsetting – the thought of anyone rifling through or taking those things must be painful – I can see why you feel violated. Then there’s the fact that your parents decided to do something about this situation without telling you about it. I think it should have been obvious to them that you would’ve liked to hear about this beforehand, rather than after-the-fact. So, either they simply didn’t consider their own daughter’s feelings on the matter, which isn’t very nice, or they actively went behind your back, which also isn’t very nice. I can see you feeling hurt and betrayed by this.
On the other hand, from a rational standpoint, you abandoned those things. Yes, you were forced to leave the property, but if it was possible for your parents to return and claim things, it was possible for you, too. Since you didn’t do that, the items became up for grabs. And your parents happened to grab. It could have been anyone. They were no longer your “personal belongings.” If you feel any loss about them, that’s your own fault: you should have done something about it when you had the chance.
Summary: You have not been thinking things through or acting logically, but under the circumstances, I think your behaviour and emotional responses are totally understandable – which is why I think your parents were callous to do what they did.
Super-summary: You’re both wrong.
Solution: Talk it out. Explain to your parents how you’ve been feeling about this whole foreclosure thing. Explain how you felt when you found out about the treasure hunt. Stay away from blame language and just talk about your feelings. If you do this in a humble, sincere way, ideally your parents will realize the hurt they caused you, realize that maybe they should have predicted your being hurt by the treasure hunt, and apologise for not talking to you about it before-hand. Then, ideally, they’ll offer to you any of the items that you still want. If it doesn’t go this way – if your parents remain adamant that they did nothing wrong – well, at least you’ve expressed yourself, and now you know a little something more about your parents: they’re callous. Chalk it up to a learning experience, mourn the loss, and move on.
P.S. I don’t see what the hoarding thing has to do with any of this?