Have you noticed any coolant loss previously? The reservoir is pretty small on these cars.
I assume you're certain it's coolant and not condensation?
Also, there is actually a coolant line going to the throttle body (for warmup) which is just downstream on the intake. I've never seen the TB dissaessembled but it might be possible for a leak there to contaminate the upstream intake, although that would be going against the airflow.
But most likely what Litespeed said.