moving iTunes library and missing files

[bcoleman001]

I keep my iTunes library on an external hard drive. I had downloaded some albums to my macbook and when I tried to copy the album folder from the macbook to the external hd the files on the external hd were deleted and replaced by the folder with files I was copying instead of just adding the album files into the artist folders. Is there anyway to recover those missing files? Thanks for any help you can provide!