Would the wrong oil cause this problem within a week

A week after we had our hyundia tuscan serviced (not at a hyundia garage) it developed a serious knocking so we took it to the local hyundai garage as it is 3 years old and still under waranty. They told us that the oil used is not a recommened oil by hyundia and I have had to prove that the previous services the correct oil was used this I have done as I had the receipts. After checks they have said it is the piston shells and my question is even if it was not a recommended oil would this cause a problem to the piston shells in a week?