No, the site was never indexed. I checked almost every single day of the 5 months. It wasn't indexed before the robots.txt change, and it wasn't indexed after, either.

And none of the other sites running that robots.txt were de-indexed. In fact, they all continued to get new pages indexed.

Just because I don't immediately accept the first suggestion you make, and provide evidence as to why that suggestion is not the cause, does not mean I think you're incompetent. It means I think you were being dismissive. ;)