I ran into an issue earlier where I couldn't deploy because of some MODULE NOT FOUND error where it couldn't find node-uuid. Unfortunately for me, this deploy was one where I was upgrading a lot of versions of things. In looking at the build logs on heroku I found one different was that it was using a newer version of Bower to install dependencies. On a hunch I switched the buildpack to point to the commit ef7a9876ec12d01ccfa78d1fc7be4bca103231eb instead of run-bower/HEAD and deployed with that and I found that it worked. It might not be the version of Bower, but somewhere between those two commits something went wrong. This would be a perfect time to use a git-bisect to figure out which commit went wrong.
Let me know if you can/can't repeat this error. We're deploying with ruby-2.0.0 and rails-4.2.4
I'm a big fan of this buildpack so let me know how I can help if you need it!