Again that is open to perception. It sometimes takes me a week to answer an email & often if its not super imortant, I'll put it aside to answer it later then it's forgotten. I figure if its urgent they will ask again.
Did Billy send one email, two or ten? Did he just ask basic questions or were any emails marked urgent? Did a day go by, a week or a month? Maybe Mr. Fong was out of town for 2 weeks & just got back. Maybe his wife just had a baby. Maybe his spam filter caught Billy's email or vice-versa.
It sounds like a 1-2 man show maybe, and if that's the case depending on the content of the email & how much time transpired indicating "I never received a response" might be interpreted as "I never received a response in my acceptable timeframe". I can go on and on.
This is another reason to be thankful Billy took his time to do legwork, but if you have further concerns one must do their own work to base a trade decision on because perceptions vary from person to person. Taking two days to answer might be too long for some, whereas I would be "What's the hurry Bub".