If you're on really shitty acquisition terms like this, to the point where you are getting no payout for your hard work, one way you can get a small payout is to negotiate your employment contract with the new parent company to be very, very good.

Make sure they give you and all employees a nice big sign on bonus and salary. They can deduct that from the proposed acquisition price.

Is it ethical? I say yes, you should get paid more than $0 for your hard work to be handed over. Should the investors get a payout too? Yes, but they shouldn't be getting 100% of it, ever.