Q. I sold my house and cars before Pesach on an early mechira because we were going out of town. Sadly when we returned I found out that one of our cars was stolen. The insurance is B”H replacing it, but I have my misgivings, since after all it was not my car when it was stolen. It belonged then to the goy then, can I still collect?

A. Horav Shlomo Miller’s Shlit’a opinion is that you should check with your Rabbi if he actually sold the car itself or just the chometz therein. Many, even on an early mechira (sold before the beginning of day fourteen to avoid bedika), only sell the chometz in the house and not the house itself, to avoid questionable issues of reinstalling the mezuzos (See Lechem Haponim 114, Piskei Teshuvos 448: 12).
Shaarei Tzion (O.H. 1: 12), debates, if one can on Chol Hamoed use a vehicle that was sold and the extent of the sale involved. He rules leniently in regards to using the sold car, since he does not consider it to be a complete and legal sale, as opposed to the chometz. (See also K’ruei Moed p. 22).
Horav Shlomo Miller Shlit”a also indicated, that even if the car is to be considered legally sold, since it remained without insurance for the buyer, it may be a case of mekach tous or a mistaken and misguided act of acquisition for the unaware and now affected Gentile purchaser, resulting in the car itself not being sold.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a