The incident happened about 9:30 a.m. PT Wednesday near the Skutz Falls turn off.
"There were two logging trucks travelling, both fully loaded ... from Lake Cowichan to Duncan in an eastbound direction, in close proximity to one another," said RCMP spokesperson Cpl. Darren Lagan.
"The first of those two trucks — a rock appears to have dislodged or fallen off the truck, bounced off the highway and entered the windshield of that pick up truck."
The driver of the second logging truck didn't stop. Lagan says it appears he didn't know about the incident.
Investigators are now contacting trucking companies in hopes of identifying the driver.