Yeah IMO it looks like they are both in comfy clothes heading out somewhere where they don't plan to be gone long. For one, I don't think anyone would purposely leave their cell phone behind if you didn't plan to come back that night (unless she forgot it? But most younger people always know where their phone is). Also, I don't know the ins and outs of COVID restrictions where they live, but there just isn't all that much to do right now, at least where I live. No bars to go hang out at, etc.
Like someone above mentioned, maybe a quick drive to a gas station for snacks or something? And knowing they had a dog and had not left any plan in place for someone to care for that dog, I feel they ran out for a quick errand or maybe even just a drive to get out of the house and had every intention of coming back within an hour or two (or less). MOO.