ruby on rails - Assets showing on localhost but not heroku -

ready incredibly confusing?

http://localhost:3000/assets/facebook.png 

this shows fine. when push heroku, of other assets appear except facebook.png. can't explain it, can't figure out. else works fine.

i've run

rake assets:precompile 

so isn't issue. fun, deleted gemfile.lock, bundled, , pushed again. there's nothing can see or find makes me think image isn't making up- isn't somehow. ideas, thoughts?

answering 1 of questions! after hour of searching around found rails 4 hates me, or rather, hates old code i'm running. listened heroku during push, , suggested use gem rails_12factor. looked @ git here: https://github.com/heroku/rails_12factor , turns out addresses issue. locally works peachy, when go production rails using nginx. rails_12factor instead routes assets pipe, makes more sense anyway.

i hope solution of use else out there, because sure frustrated me couple of hours (even before posted q earlier ;) )