That's the bad part of buying a used car, unless you know the car's history. My wife bought a 1 year old Saturn SW2 Wagon with 33,000 miles on it in 2000 from our local Saturn dealer. It consumed oil at the rate of 1/2 quart between oil changes and was told that Saturns do that. By the second year, it was using a quart between oil changes.
Then one night I decided to change out the speakers in the front doors and found silt inside the doors. No wonder the speakers sounded bad. I traced the silt line and it covered the bottom of the dash and most of the engine. The car had been in water, from the bottom of the rear doors on the driver's side to the top of the hood on the passenger side.
Found the spark plugs completely packed in silt. Had to vacuum them out before I took the plugs out to replace. Plug wires were pretty gross too. Dealership said they didn't notice any of that... even though they had done a "44 point inspection".
The engine finally seized at around 48,000 miles and had to be replaced. I found a used engine with about 40,000 miles on it and installed it. Our Saturn's still running, and now has 165,000 miles on it. Not burning oil, but it does have some strange electrical gremlins, probably from the immersion. We use it mostly during Winter as our sacrificial anode car to the salt gods!
Stuff like that happens. It's a chance we take anytime we buy a used car. If you fix your Vibe properly, it should last a long time. They are basically a tough Toyota Corolla.
Hope you can get it fixed. Good luck!