This is an update to my post. I’ve received a response from Hubspot support and they have come across this issue with other customers. This was Hubspot’s response:
“We have seen some instances where customers have had these false detractor responses as well. Most of the time, this has something to do with the client’s email security settings. The way that some of the email clients work, is the software automatically clicks on every link in the email to check for malicious content. Since the 0 Score is the first link that shows up in the email under the scoring section, HubSpot might be mistakenly recording that as their “response” as that.”