“Having read your column on the Internet, I would like some advice on the following situation regarding my immigration status. I legally emigrated to the U.S. from Ireland in February 1983 and resided in Arizona until I returned home in December 1996. I now wish to return and work and ultimately retire in the U.S. I had/have a green card status and I am also being tentatively lured back to a job by some of my previous Arizona work colleagues. Having done some research on the matter, I see that perhaps I should have filed Form I-407, but alas, I did not. What is your advice regarding my return to the U.S.?”
As you’ve resided outside the U.S. for close to 11 years, the green card in your possession is no longer valid as a reentry document. 
Those who are in possession of a green card are obligated to make the U.S. their primary place of residence, and they must also file U.S. income tax returns. Clearly, those requirements don’t apply in your case.
The I-407 form you refer to is filed by those who wish to relinquish their permanent resident status. Once the form is processed, a stamped copy will be sent back to the applicant by the U.S. Citizenship and Immigration Service (USCIS), and the person will then be permitted to re-enter the U.S. as a temporary visitor.
Though you did not file the form, this will not prohibit you from returning to the U.S. as a visitor – with visitor being the operative word. You say that you wish to relocate and retire here, but that may well be a difficult goal to achieve.
Is there a possibility of employment sponsorship from your old colleagues in Arizona? That may be one avenue worth pursuing, if you possess certain job skills and/or a university degree.  
You don’t mention any close U.S. relative connection, so we’ll nix that as a route of return. Then there’s the annual green card lottery that takes place every fall which allocates 50,000 visas, but millions of hopefuls from all over the world apply so the chance of success are slim.
You may be keeping abreast of the immigration debate in the U.S. that’s now ongoing, and which will hopefully result in new reforms that will include an annual guest worker program. This is something you should also keep an eye on.
Hopefully the company you left in Arizona will be able to provide some sort of sponsorship for you, as it seems to be the only way available for you at the present time to legally return to the U.S. As always, good legal advice is a must, so make sure and retain the services of an immigration lawyer if you do this.
Your letter is quite unfortunate really, and should serve as a lesson to all those with green cards who refuse to either safeguard them for the long term, or better, pursue U.S. citizenship.
You lived here from 1983 to 1996, and presumably a good chunk of those years were spent as a green card holder. After five years of permanent residence here you could have applied for U.S. citizenship.
Naturalized citizens can leave the U.S. and stay outside the country for any period of time without worry about returning. If you had only taken that step when you still lived here you wouldn’t need any advice at all.
We know that this column drones on and on about the importance of applying for U.S. citizenship to the point of boredom sometimes, but questions like the one above show that the message can’t be hammered home enough. 
If you’ve got a green card, and you want to leave the U.S. for the long-term, either obtain U.S. citizenship before going, or at least apply for an I-131 re-entry permit with USCIS before departure. Visit for information on how to take this vital step.