Sequential reordering error fix?

Hello all-

The title of my post is slightly misleading since I'm not really experiencing an error per se, but more of an obstacle that I can't seem to resolve.

So, I was working on a book of photographs over the summer - I'd be working with a collection of images in lightroom that were ordered to match the ordering of images in the book layout. I'd export a series of files in Lightroom with a three digit sequence number appended to the very front of the filename, ex: "001_XXX_.TIF"

Naturally, the ordering of these images changed here and there, but with disastrous results! I'd manually go in and rename the files by hand because I couldn't find a way to change only the sequence number appended to the front of the filename.

Now - my book is completely done, but I have many folders with the book images (a folder of flattened RGB's, a folder of layered RGB's, flattened CMYK, layered CMYK)... all identical to one another, but with incorrect sequencing. For example: the file formerly known as "021_xxx.TIF" (or the 21st photo that appears in the book), has become the 23rd photo in the book. To my knowledge, I'm completely screwed here... and will probably have to rename by hand. If that's the case, I'll have an intern do it... but thought I'd ask here first.

It's important for me to archive this project with the filenames actually matching up to the order of the images in the book.

I'd really appreciate any help and will provide anything needed! I've attached one screengrab here.