I am 54, have a k pouch (abdominal pouch with a stoma) and have had 6+ hernia repairs (most with mesh) and over 18 abdominal surgeries.
I have a 'somewhat' flat stomach if you do not count that one side is sort of flatter in a different spot than the other
I had some cosmetic surgery to redo my mainline scar (used to be the St Andrea fault), reduce 3 old stoma sites and remove a fat pack on the right over my pouch.
No where near perfect result (it took 3 surgeries to get to where I am now.... )but I can live with this (I am 54!).
I walk a lot with a heavy backpack. Mostly uphill, so I tend to hold my abs in tight while climbing, pull in butt and straiten back...I have noticed a remarkable result. It is now a natural reflex. I also 'flap' my arms a lot while walking and it has helped with those 'wing' things hanging off of them! (Paranoid that one day someone is going to film me and put it on a social network site! Yikes!!!)
I no longer workout in spite of the fact that I have been a fanatic about it my whole life. I have integrated my workout into my lifestyle and am seeing steady results.
You may never have a perfect 6pack again, or you may need some help to get there but do not ever feel guilty about retainning a bit of vanity and dignity. For me it was part of my healing process.
When I do not care about what I look like I know that I am down but when I do care about appearences it means I am doing better.
Good luck getting those abs back
Sharon