Hi again! You were totally right, that's my mistake. It turns out the textures didn't pack properly into the .blend file after all. I am so sorry for the runaround!
I just uploaded a separate "textures.zip" file to the download page. You can grab it now, unzip it, and use the (File > External Data > Find Missing Files) trick in Blender to link everything up.
Thank you so much for your patience, and let me know if it's working properly now!