I-551 evidencing permanent residency

I got my green card in this August but not my wife. She was dependent but she was accidently in a separated case. She had her green card interview in this Sept. An immigration Officer stamped her passport and granted her a temporary I-551 evidencing permanent residency for one year. She was told her formal card (regular card) would have been mailed in one month. But we never received. How can we facilitate her process to have her real green card? She called USCIS but she was told she needs Receipt Number. Unfortunately, we might not make a copy and an original copy gave to the immigration officer. Could you give us some suggestions? Thank you very much for all your input.