Who gave me a negative trust here? I didnt even know what I did.
It's pretty straightforward; you said that you'd keep someone else's coins if they were mistakenly sent to you, proving yourself untrustworthy.
If you want more information on one of your trust ratings, you can read them yourself (the way I did... not hard) and/or you can PM the person who gave it to you (in this case, DannyHamilton) and ask for more information. This one is pretty clear-cut though, so I don't think you have much of a chance of getting it removed.