I sent my birth certificate in with passport paperwork, will they give it back?

I went to the post office to get my passport and brought in my birth certificate. The lady stapled my birth certificate to the paperwork and sent it in. I assumed they’d send it backk with my passport. I received my passport today, but no birth certificate. My mom is all sad because it was the one she’s had since I was born, blah blah blah… How do I get THAT copy back?