You tread very carefully. Maybe some paperwork has been signed saying whose property the project hypothetically was - that would have to be read very carefully.
All contractual agreements clearly define roles and responsibilities which, unfulfilled, void any obligation by the other party.
On one occasion I made airports for a guy that had large areas of what he called "photoreal" scenery. Immediately after negotiating payment, he locked me out of his server and access to the work I had stored there. I immediately uploaded every airport to Avsim as freeware.
More recently I was in a similar situation to yours, with a company in the Middle East. They were doing a "proof-of-concept," or "simulator prospectus" of some desert islands they wanted to terraform and decided to present the idea using P3D. It was an awesome opportunity to learn about the country, the culture and how they do business - and for the last one, I use awesome in the way you'd describe a thunderstorm, or a very close fly-by. 'Awesome, now I have to go change my pants.' We had NDA and contracts and all that - and through it all I knew their best chance of enforcement was to polish those scimitars, load everyone in the Lear and come to my house to hash it over, which they were perfectly capable of doing.
I was to be paid in installments as various stages were completed. The first stage was a rousing success from my perspective and when it came time for the next installment, payment was not forthcoming. They hemmed and hawed, "the sheik is vacationing in Dubai," etc. I was having none of it; no money no production, plus I will release the unpaid work to the community, I told them. Finally I threatened to take them to the State Department. To be honest I didn't even know what that entailed. I most assuredly would have pursued it, but within an hour or two of that Skype message, I had a Paypal notification. The weirdest part to me, was that the next day, it was business as usual. This went on for two cycles and I finally decided that this is how they negotiate. Crazy huh? Since I was indeed paid the agreed amount, I have honored our agreements. It's too bad because I made what I thought was some really cool stuff 99.9% of the world will never see.
Had I not been paid, as what appears to be the case in your situation, those agreements would have been null and void. In fact, I would have had a duty and resolve to recover on my investment, as I suggest you do. I would like to see you form your own team, recruit if necessary and get something back out of your investment. However if you compensation included installments, you probably only own what was not paid for.
