请教 PJiang 老师: About Returned Green Card

I-485 bing approved early this month and got an e-mail said: CARD RETURNED AS UNDELIVERABLE, BEING HELD FOR 180 DAYS. Checked case status online, showed same thing. However when Called USCIS 1-800-375-5283, the officer said I should wait, the card will come to my mail box in several days, because on his screen didn't show that kind of things, it was showing card being sent. So he refused to do any thing to resend the card. PJiang 老师, please me, what should I do? Thank you.