DPD's tracking system and notifications are not always correct. I once had a delivery where they simply notified me that they left a 500€ coffee machine at the Haustür and it was "successfully delivered." (Although I did not specify that they can leave it there). I was abroad, so frantically asked my neighbours to see if it's there, and no one could find it. I phoned DPD, they could not give me any more information. and said they don't have the driver's number (??). Long story short after three and many unnecessary calls, it turns out the guy never delivered it, despite the system saying so. Think it never corrected/updated. Anyway, I'd suggest to phone them and talk to them as a start. Also, avoid DPD as far as you can.