Sarin is a clear, colorless and tasteless liquid that has no odor. It can evaporate into a gas and spread into the environment. Because it evaporates quickly, the threat is immediate — but not long-lived.
The threat would have been gone pretty quickly, especially in that climate. Sarin is not like chlorine or other ground-hugging chemical weapons that linger and collect in low points. It would dissipate pretty fast and at low concentrations easily go unnoticed. Handling someone exposed to sarin is not dangerous after relatively short intervals.
A relatively short interval of days. As opposed to other nerve agents that are in a class called “persistent”.