How so? Why would there be any expectation that sales would spike in the proximity of the app being a featured freebie? Does the grocery store sell more chocolate milk before or after a sale?
I would imagine quite the opposite really.
However I would revisit the situation in a few months. The app world, especially on Android, is very much one where word of mouth rules. "What app do you guys like for managing/listening to podcasts?" Having a lot of people who now have a vested interest in this app (because they think that they got a deal on it, and that it has monetary worth that wouldn't be there if it was just a normal trial or long-term freebie) yields a lot of people who may very well promote this app.
We'll see.
This whole entry sounds a little bizarre, however. The author got exactly what they should have expected. Where is the rot? There is a unexplained spitefulness that I'm just not understanding.