We did lose a fridge full of food once. On our way out for the weekend, my wife opened the freezer to grab ice to pack the cooler. She left the freezer door slightly ajar and grabbed the cooler and threw it in the car and we left.
We came home on Sunday to the fridge and freezer completely ambient temp and had to toss everything.
If we had a mobile alert on our phone, we could have turned around and closed it just fine, or asked our neighbor to.
Some people have family or close friends who have copies of our keys to deal with just such a scenario (or to water our plants when we're away on a longer holiday).
Ok, I’ll bite. What do you do? Your phone has just told you the fridge door is open. Now what? You aren’t at home, so you can’t close it.