How can a car blow a rod if there is oil in it?
It may have been abused by being driven too aggressively.
Improper fuel, coolant in the cylinder, there are several possibilities.
Coincidence or old age.
Fitigue, wear, abuse, or a defect in the part.
Tester
It got tired of going up and down! So, it broke it off.
About 30 years ago a long time friend of mine decided to get into racing at the local 3/8 mile dirt track and ran Ford small blocks.
He would have a crank turned .020, install a set of .010 oversize bearings, and proceed to throw most of the rods on Lap 1; although admittedly it was a fast revving engine while it held together. One time he did manage to make it about 2 laps before exploding.
Just use that analogy to think of wear. 
Year, make, model, mileage?
Occasionally, in mass produced engines, a defective part can sneak in. Did the rod itself fail or did the bearing at the big end fail? Now and then you see where a ROD BOLT fails, leading to a big mess…But forged steel connecting rods very rarely fail (break) by themselves…
The car that blew the rod was a 1999 Toyota Camry. The car was serviced by the Toyota Dealership as it should have been. The rod blew in July 2007. Toyota found no oil gel build-up – absolutely sparkling clean.
Some time has passed, huh?
The usual cause of a thrown (correct term) rod is:
lack of oil
high mileage, low oil pressure, etc. ususally preceded by noise for some time.
overrevving the engine
A examination of the damage and the bearing on that rod should reveal exactly why it came loose.
yes definitley mine did it ended up buying a new motor was cheaper than fixing the rod.
Is the engine in this Camary the I4 or V6?
When I worked for GM back in the mid and late 80’s, we used to have the shop full with the 3.8L V6 with spun rod bearings all the time. It was crank kit city for a long time there.
transman
Speaking of thrown rods you should have seen a good friend of mine’s race car after a couple of laps on the 3/8 dirt track.
A small block Chevy that let 3 of them go at once. Two came around underneath and cut the oil pan and one of the motor mounts in half and the remaining rod went through the camshaft, engine block, aluminum intake, chopped off the rear float bowl on a Holley double pumper, and put a softball sized dent in the hood.
Transman, posted a question on another ahem forum for you.
On a car that old you would have to consider the wareing down of the main bearings. With cars like Toyota and Nissan you can be sure of expecting this to happen unannounced. I don’t know why but domestic cars usually give some indication that something is going wrong internally. Sounds like the guy who recommended a total rebuild (A “short block”)is on the right track. But if you can afford to, spend the money you would spend on a short block as a down payment on a newer car. Currently the car market is great for the consumer because the dealerships need to sell, sell, sell to stay in business.