Tibor,
I hope you can recoup some of your loss by either depreciating or otherwise showing that you lost money on this deal come tax time.
I am sorry the deal did not work the way it was supposed to.
For those in the future who read through this whole thread, I hope one of the things you take away from this disaster is that it is worth the time up front to make a detailed written contract.
This can include an agreement about how the parties divide risk if the value of the stock declines, becomes sick, disappears or is otherwise no longer available as part of the deal.
It can include apportioning costs such a feeding and vet care if necessary.
It can put a specific time frame on the venture.
Contracts can be modified, but one can write into the initial contract that such modifications must be detailed and agreed to in writing by both parties.
This thread is not the place for a model contract, but I would be glad to help put one together in the forums if anyone has interest and starts a thread there.
I'm really sorry this happened. Business is tough going right now for many, we should stick together in hard times.