Anonymous participant - It is clear that the officer didn’t realize you had a visa. Since the majority of people who arrive at the airport arrive visa exempt, it is understandable why he/she thought this. It is always best to inform them up front that you have it. If he/she didn’t have issue with you entering too much, they probably would have given you a 60 day visa exempt stamp. Hopefully you would have seen it and not left the airport with it.
Ok, maybe you can go on the last day, but it looks like it took then 15 days to consider. This poster a few weeks ago received a 15 “under consideration” stamp while they review.
HCMC consulate is known for asking this. Look at the other posts over the past few weeks. Did you say on your application that you were employed in any way?