cannot find module 'mongdb' heroku mongoskin - bash

Question

My app is working find locally, but when deploying to heroku one of my modules can't be found. I used a .gitignore file to ignore the node_modules folder and allow heroku to install the proper dependencies. When i run the heroku open command and search the logs using heroku logs --tail it shows this error.
The error i get is:
2015-10-21T14:42:58.415140+00:00 app[web.1]: Error: Cannot find module 'mongodb'
2015-10-21T14:42:58.415141+00:00 app[web.1]: at Function.Module._resolveFilename (module.js:336:15)
2015-10-21T14:42:58.415142+00:00 app[web.1]: at Function.Module._load (module.js:278:25)
2015-10-21T14:42:58.415142+00:00 app[web.1]: at Module.require (module.js:365:17)
2015-10-21T14:42:58.415143+00:00 app[web.1]: at require (module.js:384:17)
2015-10-21T14:42:58.415144+00:00 app[web.1]: at Object.<anonymous> (/app/node_modules/mongoskin/lib/index.js:14:13)
2015-10-21T14:42:58.415145+00:00 app[web.1]: at Module._compile (module.js:460:26)
2015-10-21T14:42:58.415145+00:00 app[web.1]: at Object.Module._extensions..js (module.js:478:10)
2015-10-21T14:42:58.415146+00:00 app[web.1]: at Module.load (module.js:355:32)
2015-10-21T14:42:58.415146+00:00 app[web.1]: at Function.Module._load (module.js:310:12)
2015-10-21T14:42:58.415147+00:00 app[web.1]: at Module.require (module.js:365:17)
2015-10-21T14:42:59.337084+00:00 heroku[web.1]: Process exited with status 1
2015-10-21T14:42:59.348953+00:00 heroku[web.1]: State changed from starting to crashed
locally my app structure is as follows:
app/
config/
node_modules/
..
-mongodb
-mongoskin
..
public/
When I search the heroku directory using the bash I don't see the mongodb module. What could be the issue?

Answer 1

I've figured out the answer. I deleted the node_modules files locally and ran npm install again and node showed this warning:
npm WARN peerDependencies The peer dependency mongodb#~2.0 included from mongoskin will no
npm WARN peerDependencies longer be automatically installed to fulfill the peerDependency
npm WARN peerDependencies in npm 3+. Your application will need to depend on it explicitly.
I had to declare the mongoskin dependency on mongodb explicitly in my package.json file for mongoskin direclty like this:
"dependencies": {
...
"mongoskin": "2.0.3",
"mongodb": "^2.0.46",
...
}
I pushed it to heroku and it worked.