I just wanted to update to say that I just got home. The one who I was worried would have died while I was at work is up there rocking and rolling, and it looks like it's almost completely worked around the crown of the egg.
Thank you all so much for sharing your experiences and knowledge. I know I only have a handful of posts on this site, but it really is my first destination when I have a question about my chickens (usually my question has already been answered somewhere, but this morning I was so frantic I couldn't make my brain take the time to search through the forums). Thank you for the support!
Ok good! A zip (not a pip) chick should be all way zipped around and out of egg in less than an hour.