The river used to disappear into "swallow holes" in the river bed, caused by the permeable chalk bedrock beneath, before reappearing above ground further downstream, and this might have explained the issue in the past.
But during the construction of the A24 Mickleham Bypass in the 1930s, most of the holes were concreted over, meaning its disappearance on Friday is a mystery.
Judy Kinloch, who lives near the river at Lodge Farm in Mickleham, said: "The swallow holes are still there but they're not taking in water at that rate and, if they were active, they would be doing it all the time.
"The point is that it was here one day and gone the next. That's the odd thing. Somehow it has suddenly disappeared."
According to farmer Nick Bullen, whose land the river runs through, a similar thing had happened the week before – but on both occasions, the river reappeared within 24 hours.
He said: "I came over the bridge on Monday afternoon and thought, 'that's a bit strange'.
"I didn't think anything more of it but then on Tuesday morning it was still down so I phoned the Environment Agency.
"For the time of year and the amount of rain we've had, it just doesn't add up."
Dorking and District Angling Society owns fishing rights at many points along the river, and members are concerned about the Mole drying up.Secretary Paul Huggins said: "The angling society is concerned about the conservation of the river environments. All the fish we catch are returned unharmed to the water. SOURCE