Michonne figured out Rick was alive when she found proof on Bloodsworth Island: his boots, plus a phone with a sketch of Michonne and Judith and Rick’s name on it. Those clues convinced her that Rick survived the bridge explosion and had been alive long after everyone thought he was dead.
What changed
Before that discovery, Michonne only had the assumption that Rick died in the bridge blast. The boots and the phone were the first solid evidence that pushed her from hope to certainty.
Why it mattered
The phone was especially important because it suggested Rick had left behind a personal trace connected to Michonne and Judith. That’s why she decided to leave and search for him herself.
In the story
- Rick was believed dead after the bridge explosion.
- Michonne later found his belongings on Bloodsworth Island.
- The discovery made her realize he may still be out there.
TL;DR: Michonne didn’t see Rick alive directly; she learned he was likely alive from his boots and a phone with a drawing of her and Judith, which confirmed he survived the explosion.