Q: had car for 5 days, then suddenly stalled leaving me stranded. Engine wont turn over to start

mechanic says some head valves were loose so he ordered new parts and replaced the head. Then he took the car out for a test ride,15 miles away. He says the valves were still making noise, so this time it must be bad parts from the store. Then he checked the timing belt from beneath the car. Thats when he says he noticed oil all over under the car and a hole in the oil pan. He claimed that I must have hit something that busted a 1/4" hole in the oil pan which is the cause all the engine problems. He suggested that my insurance would cover all repairs since it was a"road hazard"that caused the damages. However I’m uncomfortable accepting blame and claiming on my insurance, since I strongly disagree that I hit anything to cause a hole in my oil pan. It’s very suspicious that a mechanic didn't notice the hole in the oil pan until after his test drive. Would a busted oil cause: low dipstick reading, low oil pressure gauge and lots of oil residue or noticed before initial repair/test drive?

My car has 77787 miles.
My car has an automatic transmission.