Already received GC; but SR response concludes lost in mail

[duggils1]

I already received my GC in the first week of Jan. But today I got a letter from USCIS to my service request from Dec 5th, that says

"...you have notified us that you have not received it and the post office have not not returned it to us. We must conclude that it has been lost in the mail. Therefore, you will need to file a form I-90 to replace your card..."

I have never notified them that I have nor received my card. And I have the card in my hand with me. I am puzzled as to why I received this kind of response to my SR.

I called the Texas service center today and the rep told me to ignore the letter as I already received the card. But I am not confidant about what they say anymore because they have totally lost their credibility.

I am traveling outside the country in a couple of weeks. Now, should I be concerned? I don't think I should be because I have my card with me. But I would like to know if anyone out there faced a similar situation and love hear from you gurus out there.

Would anyone recommend that I get my passport stamped as well, just as a back up? Do they even stamp your passport if you already the physical card?

Thanks in advance.