I biked to school today with my bike in perfect condition. Locked it up and went to class. When I went to my bike a couple hours later, the derailleur was bent out of position. My bike's front gear was at 3, but the derailleur was forced to the first/smallest sprocket. Now I can't shift gears on my front wheel as the derailleur won't move. Is this fixable? Or do I need to buy a new derailleur. If it's fixable, would it be difficult for me to do it myself out should I simply take it to a shop?