Robert Gapin was killed in the raid on Fredericksburg. I just published a book on the 1st Indiana Cavalry, Companies I and K. Gapin was a member of Company I from Terre Haute. You can get a preview of this book at http://www.lulu.com/product/paperback/the-bracken-rangers/14690592?productTrackingContext=search_results/search_shelf/center/1
I'll post the info I have about Gapin in a separate message. There was a man named "Otho Gapen" in Company K, from Indianapolis, and I wonder if there was any relation.
You can also contact me directly at MiamiRob@AOL.com if you want to. You don't need to buy the book just to get info on Robert - I am happy to share any info.
Rob Stevens