The very first Cibachrome (as it was called then) print that I developed I did something similar. I bought the little 4x5 discovery kit or whatever they called it, which had a 4x5 paper drum and either 20 or 25 sheets of 4x5 paper and chemistry. The paper was packed with the usual cardboard, one side of which was quite smooth. I had never worked with paper in total darkness before, and didn't know how heavy the paper was supposed to be - I exposed and processed the cardboard. Of course I was a teenager at the time.
I had an important roll (shots of my fiance's grandmother's birthday party) not go through my Pentax LX because of bad loading, something I had NEVER done. This was last year, and I've been shooting film from 35mm to 4x5 off and on since the 1970s. When I got the LX I was used to my old Ricoh's film loading system (which is probably the best and easiest ever, short of the automatic "close the back and the motor loads" of later motorized cameras.) I kept trying to load it like the Richo because the takeup spools look similar, and frequently had problems. The manual didn't help.
After I got back a blank roll of Portra 400 from Dwayne's I figured the thing out. It's actually quite easy, but of course it was too late for that roll. The thing is, while they look similar, the slots on the Ricoh are very shallow, just tuck a bit of film in and it's good to go. The LX and other Pentaxes with that system has something more like little rods on the takeup spool, which won't grab a small bit of film, it needs a lot more film tucked in, but they are also very tight - I'd been missing that you really have to push the film leader under there. When you do, it loads easily - but I'd never pushed it that hard because I'd never needed to on my "loads very similarly" camera I'd had for 20 years or more. I thought it was just hard to load; to get the take up spool to grab a small amount of film I had been tucking all I could without really pushing. Of course I had apparently, in the moment, neglected to verify the rewind knob was turning as I wound each shot.
We all make goofy mistakes. If you want to truly do face-palms and curse yourself for new and creative ways to screw up, get into large format. I guarantee you'll find several amusing but painful "new" ways to screw up a shot before you start getting it really down. It's not difficult, there's just a lot of little steps and things that are easy to forget. A checklist helps at first. No kidding.
Or pull the right slide, then realise the shutter is still open from composing. There are about 50 more...........
