general problems of the 2003 Dodge Durango

I have a 2003 Dodge Durango with about 30,000 miles on it and the problem I am having is the center cap on the wheel is coming off when the car is being driven. At first I thought maybe somebody was stealing them but I now know that isn't true. After I lost two of them I decided to check them every time I get in or out of the car. Yesterday I had to go to the doctor, so before I got into the car I looked to make sure that the two center caps that were left was still in their places of which they were. When I arrived at the doctor I checked again and this time I was missing one on the rear driver side. I did not stop anywhere so I know that it had to come off while I was driving. I also called the dealer parts person to find out if they had replacements and how much they were and he told me that he has been having a run on them and that either somebody must be collecting them or they were defective. I know that somebody will get hurt badly if they get hit by one of these, especially if the person is driving at a high rate of speed. I don't know where to go from here and am hoping that you may be able to help me out. Thankyou, larry occhipinti (occh1@aol. Com) .