Yet ANOTHER update!!!!
I called the person who originally left the message on my phone about Amelia, and she has most CERTAINLY confirmed it was Amelia. She said when Amelia ran into the garage, she could hear low growls and she wasn't sure if it was Amelia or not, but now assumes that it was the neighbors cat who was out. She once again described Amelia to me in detail (including the little pooch on her belly, her pink collar, and the target striping on her side) and insisted it was my cat, not the neighbors cat. She has also agreed to set food out for Amelia and will keep a look out for her.
I'm really filled with hope, the poster didn't contain any of that specific information about Amelia besides her pink collar, so she MUST have seen her! I'm just dying to get home tonight and go and see if I can find her!