Hope you find a good solution!
These days if I'm laying something out or if I've designed a pattern on the computer, I take a picture of my layout (or print out the pattern), pop it in a plastic sleeve, and tuck that in the box/bag with my fabric pieces. In the past I used the pin-in-the-seam-allowance method and never had a problem with rusting, but I hate reaching into a bag and getting poked. I'm a wimp LOL .