Receipt lost in mail for I751

[JadeW]

I filed I751 to remove GC conditions on 9/18. I received a courtesy copy of the receipt saying my greencard expiration will be extended by 18months, 2 weeks after I filed. However, I never received the official notice. And it has been almost a month. Has anyone experienced lost receipt before?
I am planning to call USCIS after it reaches 30days to request for another receipt. Please let me know if you have done this before and how long it will take to receive the duplicate receipt.
My current GC expires in early December. I am wondering if my employer will accept the courtesy copy as a proof of my work authorization?
Thank you so much! Any insight is greatly appreciated!

[newacct]

If you presented your 2-year green card to your company when you started working, they should not re-verify you at any point.

[JadeW]

Thank you! I am actually starting with a new job in December post the expiration of my current GC.

[newacct]

Do you have an unrestricted Social Security card? If so, you can use that (which is a List C document) plus your driver's license (a List B document) for the I-9. You don't need to show your green card.