User-uploaded images not saving to media folder in production

I'm building a Django website where users can upload an image via a form that distinguishes them on the site. These are saved in the /grad/media/ folder (where grad is the name of the app).

This is the code that accomplishes this:

uni_object = University.objects.get(user=request.user)
logo = uni_object.logo
if request.method == "POST":
    form = UpdateUniversityForm(request.POST, request.FILES)
    if form.is_valid():
        data = form.cleaned_data

        request.user.email = data['email']
        request.user.save()

        uni_object.university_name = data['university_name']
        uni_object.website = data['website']
        if request.FILES and request.FILES['logo'] != '':
            new_logo = data['logo']
            image = Image.open(new_logo)
            image = image.resize((400,400), Image.ANTIALIAS)
            thumb_io = StringIO.StringIO()
            image.save(thumb_io,format='JPEG')
            new_file_name = str(int(time.time()))
            thumb_file = InMemoryUploadedFile(thumb_io, None, '{0}.jpg'.format(new_file_name), 'image/jpeg',
                              thumb_io.len, None)
            uni_object.logo = thumb_file
        uni_object.save()
        updated = True
        logo = uni_object.logo

Essentially I need to convert it into a 400x400 square, and then save it. This code will work on localhost, and the file will be saved correctly.

However in Heroku with DEBUG=False:

• The same code will not save the picture in the media folder
• Not even by saving a pic manually via the admin panel will the pic end up in media folder
• Even if the photo exists in the media folder, it will not be rendered on the site.
• The media folder is pushed to Heroku, so all pics that were on local are also present on heroku.

It's as though the media folder was totally ignored essentially, despite looking at the heroku logs I get a HTTP 200 when trying to access it:

2016-10-22T15:39:13.652167+00:00 heroku[router]: at=info method=GET path="/media/1477150753.jpg" 
host=www.gradba.se request_id=7e545ef5-92cf-406c-88c8-26d140541884 fwd="31.50.136.136,141.101.98.8" 
dyno=web.1 connect=0ms service=21ms status=200 bytes=6354

Can someone tell me why this is happening? I think the media_root is set up correctly because it works on dev.

Thanks!