I don’t think it’s hard to argue that. We have multiple people in this thread, including myself, who understand that a thumbs up often denotes acknowledgment rather than acceptance, an “OK” rather than a “yes”. If I discuss an agreement with you and then send it over, and you send me a thumbs up, I’m still going to interpret it that way and follow up later for a clear confirmation.

I can see how the buyer might interpret it as acceptance, but it’s such a vague response that it was irresponsible not to follow up, and I can’t help but disagree with the decision in this case.