Yes, it is usually bad for a young hog to be out during the day, but an adult female could be out during the day and be undertaking nest building – although it’s a bit late in the year for building a birthing nest and it tends to be more in the Summer that females may come out to get a break from youngsters. But you say the hog is a ‘new baby’. Also, unless they are already extremely unhealthy, it isn’t possible to tell whether a hog is healthy or not just by looking at it – especially from a distance.
Your post raises various questions. I suggest you contact your nearest hog carer/rehabilitator and discuss it with them and take their advice. You can explain in more detail than is possible on the forum and they can ask any questions.
You can get contact details of your nearest hog carer/rehabilitator by ringing BHPS on 01584 890801
Good luck. I hope all goes well.