If an authorised representative of a company places an order, then that company has entered into a contract. This applies even if there is nothing in writing. So, in law, you're entitled to deliver the order and demand payment or to seek compensation from them for the cancellation of the order.
In practice, however, all that the current directors would need to do would be to state that their former colleague was only making an enquiry and not placing an order. A court of law would have to decide 'on the balance of probabilities' who was in the right. Unless you could contact the former director and get his confirmation that he placed the order on behalf of the company, you would be at risk of losing out.
It's extremely rare for MustaTickl and I to be of the same mind but, for once, I have to agree with him.
Chris