Indesign CC 2014: Chapter number with title in an ePub's navigational TOC

I have a multi-document .indb file (Book) with each chapter in an independent .indd file. Each chapter has a title page in the following layout:

CHAPTER 1 (paragraph style: chap_num)

NAME OF CHAPTER (paragraph style: chap_title)

Now, when exporting to ePub, I want the navigational TOC to show entries in the following format:

Chapter 1. Name of Chapter

I have tried everything from hidden layers to conditional texts but am unable to get the results! Is there any trick to achieving this? Here’s what I tried:

1. I created a separate textbox in the chapter title page containing Chapter 1. Name of Chapter, placed it in a new layer, and made the layer invisible so as to not show it on the rendered page. The problem is, ePub’s navigational TOC refuses to reference it if the layer is hidden.
2. I created a separate textbox the same way as above but instead of placing it in a new layer, I made it invisible using conditional text. Same problem here, ePub’s nav TOC doesn’t reference it once hidden.
3. I created the same textbox with the same contents but instead of hiding it this time, I made it invisible by turning its font color to transparent. This works with the navigational TOC but the rendered ePub doesn’t respect the transparent text color and the textbox is visible on the chapter title page.

Is there any other trick to get this done? I know it’s possible because I have seen plenty of ePub books that do it. Just not sure how to get the effect.