Did you get an email confirming your purchase? There is a download link in the email
I did just as you suggested,download the file and i only see the sound track apigquest_ef (security certificate) and the game's manual
apigquest_ef.crt
Its game, cartridge image format.
certificates have the same [.crt] extension
Your OS (probably Windows) hides the extension of "known" files by default (eg windows certificates .crt) .