Kavod HaRav: I’m very sorry for not being more clear. The sale was the sale of Chometz before Pesach. I sold my chometz online. But I wasnt sure if the car was technically included in the sale of my chometz. Because I did not know where the car key was at the time, I did not check the trunk of the car before Pesach. (I could have found another way to open the trunk, but there was so much going on, I likely didnt think of it at the time.) I hope this is clear enough, and if it is not, I can try to explain better.
ב"ה Shalom, I still need more information, but I will raise a few scenarios and you will choose which one is relevant. If the answer is still not clear you can write again. Firstly, you did not mention if there was Chametz in the trunk of your car. But, I should say, a car must be inspected for Chametz before Pessach just like your house is. You may, however, use a flashlight to examine the car instead of a candle. If you had no Chametz in the trunk of your car, then obviously there is no issue of concern. If your intention was to sell all your chametz that includes the Chametz in your car. The fact that you were not able to open the trunk doesn’t prevent the sale. I hope I have answered your question All the best