Lost Episode?

Years ago my mother showed me a home movie that one of her cousins, who worked on the show, gave her of a rough cut of an episode that was filmed but never finished or aired. This was about 1975 and was on a 6" B&W 8MM reel that ran maybe about 15 minutes.

The episode goes something like this; nobody is home and Lad gets out of the yard and gets hit by a passing car. The driver of the car takes the dog to the veterinarian where be pretends to be the dog's owner and they discover he has broken both front legs. The driver of the car then takes the dog home as he intends to keep the dog for himself. The Nash family puts out a reward and 'missing' posters in the neighborhood, but in the end when Lad's legs heal he runs away back home and they find him the next morning and nobody knows where he's been or what happened.

Apparently the episode was never finished because it dealt with dognapping and there was a prominent case around that time frame... maybe some celebrity or something? Does anyone know anything more about this?