Now that I am using the invisible reCaptcha, this should not appear at all.
Are you 100% sure, talked with Google support?, becuase during my expirence I know that Google is using it for invisible reCaptcha as well if tester script is not sure about the user.
Did you take a look at this picture:
I couldn't, becuase on your site, I was able to send message without. I just put my text, and clicked sent.
I will change it back into the default reCaptcha on Monday and then see what happens.
OK, but it may show you human validator script anyway.