If the man knew the items were not meant for him, why did he go ahead and open them, and then give them to his son?
The right thing to do would have been for him to say to your gf "Hey, I think these aren't mine, I didn't buy them, perhaps there's some mistake and you should hang onto them."
As a matter of principle, don't touch what's not yours. The fact that they are sought after figures makes it that much harder to put up with what's happened.
I don't think you're crying over nothing. I'd get angry too if I were you.