finally, my case no approved

several weeks ago, i received an e-mail from USCIS and informed me that my i-485 case has been approved. but i did not get any letter and have to call CIS. they said my case has not been approved yet. however, the case status in USCIS website apparently shows:

On xx, xx, 2005, the document we made based on the approval or registration of this case was mailed directly to the person to whom issued.

i feel i was teased and 空歡喜一場 finally.anybidy has the similar experience? or give some good suggestions. thanks!