How to cancel 485 approval when no GC received subsequently

[grenamn]

Guru's please help with the following situation: Labor PD: Dec 2002, Labor approved Feb 2005, I-140 approved May 2005, Filed I-485 (because of retrogation) in May 2006 for both me and wife. Got EAD Dec 2006. Got laid off in Feb 2007 from sponsoring company and decided that I have had enough of US immigration waiting and returned to home country for good in April 2007. Changed address to friends US address for USCIS records just to make sure that any communication from USCIS does not get lost in the mail. Was sure that the employer will cancel the whole GC process. But to my suprise on April 21st 2008, received the automated email from USCIS that 485 has been approved. The I-797 approval notice of action was received at my friends US address with a note that the plastic card should arrive within 30 days. This was back in April-May 2008 time frame. Well the plastic card never arrived inspite of phone calls to USCIS to either cancel the 485 or send the card.

Can someone please educate me as to what I should do get the 485 cancelled and stop further processing of my wife's 485. I am afraid that I am stuck in a situation where the USCIS records indicate that I am a permanent resident, while I have been out of the US for 2 years and do not intend to return. The US Consulate here has been of no help. Will this have any overhang for future US visits/immigration foe me and my wife or for my children who are US Citizens.