The story is a bit suspect. A timing chain generally only breaks because the engine is sludged due to lack of oil changes, loss of oil pressure, etc. This would not be a warrantable item as far as Mazda is concerned.
A "rebuilt" engine does not have 60k miles on it. This was a used engine from the get-go and at 126k miles it's well-used.
I'm not saying the car is necessarily a bad deal but that would depend on the asking price.
A neglected engine often means the rest of the car has been neglected also.