In my time I've made just about every mistake with shooting and developing film that it is possible to make. A year ago when stumbling around some rocks with a Yashicamat attached to a tripod, the camera back opened and it took 20 seconds to get it shut ... yet I only lost half a frame (and in fact the remaining half a frame worked by itself really well)
On the other hand, last week I accidentally took the lid off a jobo developing tank to pour the chemicals in. Well, my excuse is that with a Patterson tank, you can and do take the lid off because the internal funnel forms a light seal, but not with a Jobo ! Remembering my Yashicamat experience, I covered up the tank asap and decided to develop the film anyway ... needless to say it was a waste of time and chemicals as all the images were ruined.