Secret key not available

[DUELL, BOB]

Hi,

Couple quick questions (and probably a FAQ):

1.  Attempting to decrypt a file that was sent to me by someone else, 
    I get this message:

    gpg: decryption failed: secret key not available

    Could that mean the file was not encrypted with my public key?

2.  Assuming the above it "yes", is there a command I can use to
    display what key(s) were used to encrypt the file?

This file is coming from a vendor who recently transferred some of
their operations to an "offshore" location and I'm dealing with quite
a communications delay with them.  They probably use different keys to
deliver files to different groups in my company, but that's just a guess.

Thanks!

Bob