Luggage compartment full of water!

Hi I was on the road the other day with bright sunshine and before I started driving I put something in the trunk and it was completely dry. Then I left and after half an hour driving I wanted to take my things out again and in the trunk was 6-7cm high water in it! I have to say that it had not rained the days before and I was not in the washing machine either! Can someone help me with this mystery I have no balls again my whole To have to wring things out! MA beautiful biscuits were also gone *heul* mfg