I had something similar happen to me a long while back and had to move forward using a .jpg I had posted as a WIP. I don't even know what smart objects are but it sounds like you lost a ton of work and that sucks.
I remember that sickening feeling deep in my stomach too. I feel for you and wish I had something to say that might give you a ray of hope but I don't. I do hope one of these other guys who are experts with PS know a trick or two to help you out.
If not, just know that I am standing beside you in sadness as you gaze into the chaotic fires that destroyed your hard work.