为什么移民局收到补充材料2个月了，还没发广州， 我该怎么办？

Response To USCIS' Request For Evidence Was Received
On January 12, 2015, we received your response to our Request for Evidence for your Form I-730, Refugee/Asylee Relative Petition , Receipt Number LIN14******XX. Our Nebraska Service Center office will begin working on your case again. We will mail you a decision or notify you if we need something from you. You should receive a decision or case update by March 13, 2015, unless fingerprinting or an interview are needed. If you move, go to .....
大家帮忙看下， 为什么移民局收到补充材料2个月了，还没发广州， 我该怎么办？ 崩溃了。