I second the motion. OEM and cheap aftermarket rotors can warp. Actually, any metal brake rotor can warp. Turning them will make them thinner and will probably warp again even sooner. If brake rotors overheat, they tend to warp. Really easy to warp rear rotors by leaving even a tiny bit of emergency brake on while driving. Poorly adjusted emergency brake will do the same thing, keeping slight brake pad contact on the rotors, they overheat and poof... you get warped rotors.
Just did a search on google for... "09 vibe gt brake rotors" and I got 153,000 individual 2009 Vibe GT brake rotor results in 0.36 seconds. I didn't count them, but google told me that. Your parts guy needs a good google tutorial.
Any reputable parts store or Toyota/GM dealership will give you the part numbers. Or you can google that as well.
Here's one part number I found for 2009 Vibe Gt rear rotor from Parts Geek web site (partsgeek.com):
Centric Brake Rotor - Rear
Your Price: $18.75
Quantity:
Qty Available: >35
(>35) In Stock
Part Number: 29871-05110606
Notes: C-TEK Standard Rotor
Position: Rear
Condition: New
Shipping Options:
Ground
................................Or another example on the Parts Geek site:
Centric Brake Rotor - Rear Left
Your Price: $56.25
Quantity:
Qty Available: 2
(2) In Stock
Part Number: 29871-05131875
Notes: SportStop Drilled & Slotted Brake Rotor
Position: Rear Left
Condition: New
Shipping Options:
Ground
This Product Fits the Following: Warehouse: B
Vehicle Sub Model Engine
• 2009 Pontiac Vibe FWD 2.4L 4 Cyl
All these on line parts stores offer a phone number to call, live chat or an email address to make sure the fitment is correct for your specific vehicle. These are just examples from one of the 153,000 results I got from the search.
You could also cross reference the OEM rotors from a Toyota parts counter, if you want to stay with OEM parts, or use another website like gm-partscenter.com:
Genuine Original Equipment Replacement Parts 2009 PONTIAC VIBE GT
All Vehicles - 2009 - PONTIAC - VIBE - GT - BRAKES
BRAKES
Rear ROTOR Vibe Online Price $58.06
Hope this helps out.