`/usr/bin/env: node: No such file or directory` running node on heroku

Package.json:

{
  "name": "Promptly-crm",
  "version": "0.0.1",
  "engines": {
    "node": "0.10.x"
  },
  "dependencies": {
    "coffee-script": "^1.7.1",
    "mongodb": "*",
    "body-parser": "*"
  }
}

Procfile:

web: ./node_modules/coffee-script/bin/coffee 1.scrape_in.coffee

Error is:

2014-07-24T01:03:34.341200+00:00 heroku[web.1]: State changed from crashed to starting
2014-07-24T01:03:38.334452+00:00 app[web.1]: /usr/bin/env: node: No such file or directory
2014-07-24T01:03:39.384850+00:00 heroku[web.1]: State changed from starting to crashed
2014-07-24T01:03:37.826372+00:00 heroku[web.1]: Starting process with command `./node_modules/coffee-script/bin/coffee 1.scrape_in.coffee`
2014-07-24T01:03:39.375817+00:00 heroku[web.1]: Process exited with status 127

Tried compiling my coffee and running directly. Same error.

I have a bunch of python in the same app. Can I not use both languages at once?

Update

I'm apparently using a custom git buildpack, but don't know which:

Fetching repository, done.
Counting objects: 8, done.
Delta compression using up to 32 threads.
Compressing objects: 100% (6/6), done.
Writing objects: 100% (6/6), 587 bytes | 0 bytes/s, done.
Total 6 (delta 4), reused 0 (delta 0)

-----> Fetching custom git buildpack... done
-----> Python app detected
-----> Installing dependencies with pip
       Cleaning up...
-----> Discovering process types
       Procfile declares types -> enrichment, extractor, web

-----> Compressing... done, 35.3MB
-----> Launching... done, v23
       http://promptly-crm.herokuapp.com/ deployed to Heroku

To git@heroku.com:promptly-crm.git
a8993ae..fdf5a92 fdf5a92062637bf7d5e9adb2300d31a2c5defd4a -> master