Lack of seeing things in time and not reporting them to the client

I purchased my car from Hyundai Bedfordview and I’ve been making sure my vehicle is serviced at all times at Bedfordview and Nelspruit service department I’ve even extended my service plan . End of December my car gave me problems called my insurance they collected it in January now I’m told that my engine is rusted this doesn’t occur over a day or so how is it that none of these entities never realised this had occurred one of the pipes burst and my insurance company is saying Hyundai should be held accountable for not mentioning such viable information this could have been seen when the major service was done .