I hate it when I've just put something down and can't find it... You know what's a really bad thing to do that with? A sewing needle, when you're sitting in bed. I just did that a minute ago; forgot where I put my needle, spent five minutes looking for it and trying not to move too much lest I sit on it, then found it stuck in my project.
I also have things go missing just to reappear in plain sight... I swear we have gremlins. Maybe the gremlins stole your rocks!
I really thought you were going to say you sat on it when I was reading this!!