I have a '95 Camry LE. A few days ago I had a couple cracked drive belts replaced as well as the oil pump seal and O ring replaced. The very next day I drove the car about a half a block when the oil light came on (in idle at a red light)and the engine starting grinding. Since I live only a couple miles from my mechanic, I took the chance and drove it over there. After they checked out my car, they said I needed a new water pump. They had done a 27 point check on my car the day before...why didn't they see the problem with the water pump or could some faulty repairs on their part have contributed to this problem? Please advise! Thanks so much.

Optional Information:
1995 Toyota Camry LE 4 Cyl

Already Tried:
Trusting the mechanic!