The smart speakers are a privacy nightmare, but on your phone, random apps cannot access your microphone without your knowledge or control, excluding straight up malware. There's a million anecdotes like yours on social media and none of them have held up to rigorous testing.

The fact is, most people don't realize how much of their thoughts one way or another are reflected in their digital lives, nor how good google's algorithms are. And there's also things like the frequency illusion etc.