Is this a valid reason to come in on your day off?

My employee has been out for a week due to having the flu.
Saturday and Sundays the building is mainly closed because we are off on the weekends.
I realized this morning that someone unarmed the alarm Saturday and my employee told me it was him.
So i asked him why did he come in on Saturday i thought he was sick so i was questioning his reasoning for coming in on our scheduled day off

And he said “i came in to test and see how i felt i stayed 4 hours then left”

Is that a valid reason to come in to work?
Is this a valid reason to come in on your day off?
Post Opinion