First a small item...if the specific type of ridge vent wasn't specified in the contract...and you did have a contract...right? Anyhow, if the type of vent wasn't spec'd, you really don't have any recourse with him R & R'ing your ridge vent.
However...the way he installed it is ludicrous. If I understand you, from the front of the house the shingles are contiuous from the ridge and onto the main body of the roof plane...the ridge vent is not exposed to free air?
This is silly. These vents are rated for 100+ mph winds with blowing rain. His method of installation also cuts down on the amount of ventilation allowed...most ridge vents have about 18" of free air space...your roofer halved that.
It sounds like he installed Cobra, which is a GAF product:
Cobra is an average roof vent. Not stellar in performance, yet no severe shortcomings. Inexpensive and easy to install.
Contact the manufacturer (GAF) and describe the Cobra installation to them...if it is indeed Cobra. If it's an unwarranted installation you have recourse. At a minimum, the ridge vent and shingles should be removed and correctly installed. Your roofer may whine about wanting to re-install the Cobra, but if you don't want it, tell him to remove it. He can always install it on his next roof. The stuff is fairly bulletproof and shouldn't suffer too much damage in the removal.
If you want a better ridge vent, look at Certainteed's Shinglvent II. It's one of the better ridge vents in my opinion.