No, you aren't reading the title incorrectly, and no, you didn't miss out on "Echoes of History, Part II!" The second part of Captain Rex's story actually takes place, chronologically speaking, immediately after/during today's vignette, "Secret Alliances" Mace Windu's Tale! "Secret Alliances" is actually an ongoing project by Star Wars artist Omar Maya Velazquez, and begins the story of Mace Windu from the events we saw him last. The CWR team loved it so much, that we had to include it! Omar and his team are hard at work on the continuation of this vignette, and you'll be able to check it out soon on their official site. We hope you enjoy this special presentation of "Secret Alliances!"
You can download the PDF here. You can download the CBZ file here.