Do you know why they filled it in or started to? Was there a problem with it holding water? If you can ask these questions may lead you to your next step. The other owner may ever tell you who built it. You could call them if the pond held water the first time. Good luck!
One of the neighbors thought it was dangerous as kids would frequent the pond. The neighbor started bringing dirt in to fill the pond with the owners permission. I was told that bucket after bucket of fish were removed from the pond before hand. The entire situation makes me sad, it's at least worth looking into to see if there's anything that can be done at this point.
I'll continue to work with a local company that specializes in this type of work to see what they come back with.
Thanks for the replies all!