Since the file is shown in your live site it must be synced. Just to be sure you could check your DB directly, but as I said it seems correct.
So the issue probably is on your form tab where it can't resolve the attachment correctly. So it's there but your control cant seem to find it. (Note that if you now save the page it will lose the attachment).
Can you confirm you can select the same attachment manually on your production/live site?
If so and everything still works can you compare the stored values between production and staging? Might be a path or permission issue...