Dr. James McGoldrick, a Presbyterian and former history professor at Ceaderville College has written a book (not over-long actually) in which he critiques the Trail of Blood theory at length from a historian's perspective. Dr. McGoldrick is now retired but teaches regularly at Greenville Seminary. I can find out the title of his book and where you might be able to secure a copy if you like.
The title of Dr. McGoldrick's book is Baptist Successionism, the publisher is Scarecrow Press (a division, he thinks, of University Press of America--he was not sure if he quoted that last part right when we spoke--but its not that important).
It is possible that the book is available through Greenville Seminary bookstore (they may have a few copies on hand--again, he wasn't sure). It is almost certainly available through Amazon.com or your local bookseller.