Look/feel the carpet in front of p-side.
Heater cores can leak then dump on floor. Plus you often smell coolant too when true.
That much coolant lose carpet should very wet and likely will need to remove seat etc to clean up.
Rad Cap or Tube for rad overflow can leak coolant when hot and/or suck air cooling off over night.
Iffy WP seal can leak and many cars is not easy to see when small leak.
Feel/look at WP Weep hole. Use mirrors if needed. Coolant even dry should show a clean(er) path when coolant washes the engine.
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
The Ogre's Fiero Cave