On Heroku server media files getting deleted automatically after sometimes of deployment of web application

I am surprised, after successful deployment of a Django web application on heroku server.

I am able to view the media files just after the deployment but after sometimes i am unable to view it.

Error : GET https://mysite.herokuapp.com/media/files/testing_pphTYTV.mp4 404 (Not Found) suggestions to resolve this is appreciated.....

i have used following line of code.

In settings.py file:

MEDIA_ROOT = os.path.join(BASE_DIR, 'media') MEDIA_URL = '/media/'