One time, when I was finished using a machine that had run out of bobbin thread, I took the bobbin case out of its home and put it into the machine "pocket" - - so that I would remember to wind the bobbin before I started using the machine again.
Take a deep breath, and think - - have you looked in every hidey hole in your machine? Wherever you put it, it made perfect sense at the time, you have just figured out there is a different perfect sense place! <g>
Hang in there - - it will get all sorted out soon enough.
Oh! And, by the way
you don't have to pre-wash, but if you do, just cut a small corner off each corner of your fabric and throw it into your washer/dryer - - for some reason, cutting the corners helps cut down on the cut ends ravelling, and! You will be able to remember what you have washed and which is factory fresh <wave>