[GCC LLC]

Got it figured out. I dug through the plugins and traced everything back to the following, in case anyone else runs into the same issue. Tom, you were correct in that the template hooks are not there by default in mobile styles. I also had to manually create each of the prodforum_* templates in our mobile style for some reason, but that's not a big deal.

The plugin renders the product information at the top of the showthread template into a template called showthread_above_posts. I looked for the hook inside of the SHOWTHREAD template in the mobile theme and it's just not there, so I added it in as follows:

{vb:raw template_hook.showthread_above_posts}

All is well!