No, back when I made the theme it was included in the original code. I tried running it again and I have the same problem as you do. I’m pretty sure when I made it the hamburger menu was in the default theme for Discourse and so I had just changed a couple of colors. I haven’t been on the website in three years and it looks like it has been removed. Admittedly, I have very little experience with Discourse so I don’t know how I would be able to re-implement it, but best of luck!