Unique case : I-797 Approval Notice for Approved I-140 not found in FOIA search

[indra_saha]

Hi,
I am in trouble and running out of luck. Looking for suggestions & options from gurus here; Here is my case detail :
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Priority Date : April'2009 in EB3 category India
I-140 approved On : Nov'2011
I-485 : Not applied due to priority date not current for EB3.
G-639/FOIA : Filed on Dec'2011; received the CD with pdf copy of I-140 original petition (except I-797 approval notice) on 07/23/2012;
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To my surprise, the I-797 approval notice for approved I-140 is missing in the pdf file sent from FOIA, USCIS department.
So I immediately contacted them via email USCIS.FOIA@uscis.dhs.gov and came to know that I-797 Approval Notice is missing in my alien file and that's why they couldn't include it in the CD.

But as per the online case status for my Receipt, the I-797 Approval Notice for I-140 was mailed on November 18, 2011 from USCIS Texas service center to my employer. So the document truly exist ! And my employer won't give me a copy of that !

How can I get that approval notice copy ?
I am in process of changing my employer and applying for Green Card in EB2 category through new employer. I believe that I need the I-797 approval notice for earlier approved I-140 with printed priority date to port the PD during my new I-140 application process !

What are my options available ?

Thank you for taking time out of your busy schedule and reading through my questions and providing solutions.

Regards,
Rab

[indra_saha]

Can anyone help me please with the above question !