How maddening! I'm glad you were able to get back to your project on time. When I was collecting vintage fabrics I often found old rusted in pins or staples in the fabric, sometimes you lost more fabric than you would think...
For block labels I really do like brass safety pins. I've been making little paper A1, A2, etc. block numbers but I was inspired by something another person here did, I'm looking for sets of Alpha/Numeric beads at the Thrift store. I'll take little jewelry finding rings an put the A1, etc. and then loop them through the loops in the end of safety pins. I'll still have to sort them out by alpha groups but I bought a nice little craft box full of embroidery floss at the thrift store for super cheap to do that/store them in -- now I just need to find the beads! I gave the floss to one of my quilting friends who always complains about needing "just four inches for a project".