stevew-
I have the same problem, only with my brothers. They were adopted over 15 years ago and can't find their papers.
I think you need to go (with your parents) to a regional BCIS (former INS) office, tell them your sob story and they MAY verbally give you the info. Just warn you, it takes sometimes over 12 months to get certificates reissued; hopefully you won't be told that's your only option.
Let me know if you find a way to get the numbers faster. I am still waiting on my brothers.'