This could very well be a repeat of what previously happened. Although the drain is on the passenger side, it is close to the middle of the dash, and the hvac housing does stretch to part of the driver's side, so it is possible for it to leak out of either side.
Most oil change places do not have employees that are ase certified mechanics that actually know what to look for as far as find the drain. They are high school graduates that know basically how to change the oil and other fluids.
If the hvac housing was truly filled with pine needles, which can happen if you park outside underneath pine trees, then yes the dash has to come out to take apart the hvac housing and clean it out. If this is again the case, you should be able to feel the pine needles thru the blower motor opening.
The other possibility unfortunately, is that you were taken advantage of by the repair shop.
Pine needles, leaves and other debris can enter the hvac housing thru the fresh air ducts that are located between the hood and windshield underneath the cowling. You can look into having the cowling removed and mesh placed there to catch the debris to prevent this from happening again.
With cars being parked outside, I have had them come in 2 or more times a year to have the drain unclogged due to debris