I found it!

The missing block was stuck on the quilt top I had taken to show to the class.  I had checked there the night before.  You know how you keep going back to the same place to look over and over?  I'm just happy it turned up.  I haven't sewn the blocks but I did move 2 to different positions.  The fish was doing a nosedive in the layout I did at the quilt shop.  I started quilting another quilt instead of sewing this together.