VM connect

Hi everyone, this may seem a stupid question but I just wanted to ask something regarding the VM connect. I was just curious about the devices connected to my WiFi and was wondering do devices save only when checked and connected to WiFi. The reason I’m asking is because there are a couple iPhones which have been connected in the past on the list and only time I know they’ve been connected was when my a few of my family members stayed at my house whilst I was away. Essentially If they connected whilst I was away would I be able to See it when I’m back on the list or is it only checked when I am connected to WiFi and checking. Thank you.