Thanks for the question.If there was Water on mars how come the rovers have not found caves?
To date, rovers have been sent to relatively bland (but still scientifically interesting) landscapes. Why? Because bland equals safe (to move around).
Caves have been seen from Mars orbit, however. Take a look here: https://www.space.com/mars-lava-tubes-radiation-safe.html and there is lots of water on Mars:. For example, https://www.space.com/mars-water-ice-map.html