Changing Employers (I 140 approved)

[newmemberq]

Experts,

         I believe you would have come across this question a biziilion times on this forum. After reading through some , I still dont have a clear picture/understanding of it. 

Same story told again. Here is my situation,

1) I have an approved I-140 with PD in mid 2012

2) I recently got an H1 extension through my current employer.

 

Now, I have an offer yet to be discussed for a full time oppurtunity. I understand the need to transfer my H1B to the new employer. But my question is mainly about my I140 and porting my priority Date. I did see some post about porting through AC21 but for that i believe you require your PERM documents.

 

In my case, I dont know my I-140 receipt number nor my Alien #. My current employers states and i quote " Its an application by the company and so i dont have the rights to hold that document". I am pretty sure a pretty handful of the members here would have seen this scenario.

 

Now, even to apply through FOIA i would need these info. Let me tell you what i have now with me in regards to this situation 

1) Approved LCA for Permanent Employment Certification

2) A mail from UCIS with attached document notifying about my Case number and priority date in it.

 

Now with these information in hand, what further steps can i take to initiate my transfer.