One of my 3 cats disappears frequently for up to 12 days at a time, then strolls in hungry but not thin. I think she has another home in the next village, which is 2 miles away across fields. Another cat goes off when visitors come, sometimes for a day or two. I would therefore not be too concerned in your position.
What I have is a wildlife motion-sensor camera which I put in the hall to record all use of the cat flap when I am out or in bed. I then know if I have missed a cat returning to eat and going out again. On an a average night there are 40 video clips recorded, including visits from next-door's one-eyed, three-legged, brain damaged Tom! (And I had thought they slept all night.)
It is a big worry looking after someone else's pet. As a teenager I managed to lose a friend's hamster up the chimney. Luckily it emerged, filthy, on the day of the owners' return.
I hope the wanderer returns soon.