You are not alone, we all make mistakes. I've been making Bow Tucks bags since before and after a craft fair and I'm trying to finish up the last 3 orders. Well, I decided that I would be nice to my machine and clean out all the lint before continuing to work on the last bag. I cleaned it, put the bottom part of my machine back together, but when I went to put the bobbin case in I couldn't find it. I'm serious. I had to stop what I was doing and look for it, thinking it had fallen on the floor and since it was carpet didn't hear it fall. Nope. After cleaning up my sewing table, something I had been putting off, I found the bobbin case under some fabric my husband had put on top of my table after "helping" me look for it. I do remember the bobbin flying off, and the case probably went right along with it. So, instead of finishing my projects, I spent half the day "cleaning my sewing space", and as much as it was necessary, it's not my favorite thing to do. I should have waited to clean my machine, but instead had to clean my space. By the way, I'm missing the little screw that holds my throat plate on the machine. I put all the screws on my magnetic pin holder, but it is now gone missing. Fortunately, it doesn't seem to affect my sewing as it's staying in place pretty well without it. Now another trip to the sewing machine shop for a screw, last month it was a new light for my sewing machine. Don't beat yourself up, it happens to all of us.