How many days before USCIS website shows H1B petition request to upgrade to Premium after receiving receipt


My husband was in H1B and lost his job. Before the grace period was over, he applied for H4. while the H4 is underway, he got a job and the new employer applied for H1 under REGULAR processing. The receipt for the same was received last week and USCIS status currently shows “CASE RECEIVED”. Upon our insistence to upgrade to premium processing, the employer says they have requested USCIS to upgrade it to premium as of yesterday (12/6/2017). How do we know that the request to upgrade to premium was made other than having to blindly believe the employer? Will the USCIS ‘case status check’ page show if the request to upgrade was received? If so how many days does it typically take for the update to show in the page?