Questions about Opportunity Knocks

In "Opportunity Knocks," Mona enters the house of her son in order to leave a welcome note for her son's housesitter, who is supposed to arrive there the next day. She brings with her the keys to the house in order to leave them for the housesitter who is arriving the next day. To her surprise, she runs into "the housesitter," who is in fact Dana Carvey, but she thinks it is the housesitter, even though he wasn't supposed to arrive until the next day. Carvey had broken into the house the day before by smashing the glass door and opening it. Mona doesn't ask Carvey how he got into the house, even though she knew he had no key to the house, as she was bringing the housesitter the keys so he would be able to get in. Why doesn't Mona ask how Carvey got into the house? This appears to me to be a major plot hole. Also, at the end of the movie, it is clearly not Carvey getting run into by the car, but it is clearly a stunt double, as he has a different style of hair than Carvey. However, even after the take with the car accident, the stunt double is still seen lying on the road in front of the car, even after the take has already finished with the accident. Why does the stunt double need to be there in place of Carvey, being that there is no danger to Carvey in this situation?