Also, this is why kennels exist. Just get a dog kennel that's appropriately sized for the dog and leave it in the kennel for a few hours while you're gone if they're destructive. Then, you can go back to the house and spend the remainder of the time with it. It's totally fine and a common practice. They sell the damn things at Walmart. Or, if you think that's cruel for some reason (I mean, the dog can just go to sleep on a fluffy dog bed), you can get a running line and set them up in the yard on it. Put 'em in a harness they can't get out of. As the dog's owner, Oma would already have these implements set up. He would just need someone to feed the dog and/or let it out to go to the bathroom a few times a day. It's really irresponsible of Oma to not have these things in place and to expect someone to just spend 24 hours a day at their house while they're gone, and at the last minute at that. I like the game, but this "hiccup" was not a good one. It just didn't make sense.
Don't get me wrong, I loved the payoff and how it happened over the phone with the not knowing and ambiguity and stuff, just the premise could have been better. Maybe add something like the dog is sick or something so it can't be left alone for a long time? Leaving for an emergency like he did for Ana and Hellen setting him up would still be believable, but the overall premise wouldn't be so forced if there was a reason the dog couldn't be left alone for a long time.