It was a not so easy to find coffeeScript problem. In my machine I was using coffeescript v1.4.X and heroku was using v1.6.3. I had a for own in array
that v.1.4 allowed(it shouldn't) but v1.6.3 didn't(actually it didn't show the right error but a different one which is a bug shown here).
Anyway I solved the problem fixing the coffee file but I still think its a compressor error not to fail in production ignoring errors without giving any clue of what happened.