Yes. A written contract should require a legal signature, be it a written signature or an electronic signature. Replying 'looks good to me' (or hitting thumbs up) over a text message etc should not be considered a legally binding contract, especially when you are talking about big ticket items such as multiple-tens-of-thousands of dollars in produce.

In any rate, once old mate sent the thumbs up, they should have exchanged actual contract documents.

This is why contract laws exist and shouldn't be eroded with nonsense like this.