Comment on Remove WordPress Meta Generator Tag by Rajesh Iyer.
I removed that line from single.php and it worked!! So glad to have finally figured it out. A million thanks to you.
Regarding the theme I use, you are right. It is a paid theme. I did have one issue earlier and I posted in their support forum. But before they answered, I had done a few tweaks and had got it fixed. You are right though, I should be using their support more often.
That said, I am surely going to change my theme in near future as my content increases. I shall be bookmarking your site and shall come back to you when the time is right.
You are a champ!!