I'm still not sure exactly how I managed it, but I managed to rip my floaty dress the first time out.
The tear was right next to the seam - as in the fabric of one side sheered right off. It took me a little while to figure out how to repair it so that it wouldn't show...
Enter a fine mesh, nearly same color as my skin and very very close to the slip I wear under this dress. I pinned everything back into the correct place and hand sewed along the seam and around the dots (I decided the transitional areas would show less than right through the dark patches) I cut the edges of the mesh in a wiggly line to avoid any sharp transition that might help to give it away.
Which resulted in a fix that's nearly invisible on my hand and totally invisible on my back (which, of course, I don't have any new pictures of... just trust me on this one) But! It held up all day! Win!