There is no need to be worried if you meet a hedgehog in the middle of the day. Not unless the hedgehog is laying without motionless or does not make a ball, or at least tries to scare you. If there is food available they will wonder even during a day. In the modern city or living area there is always possible to find something to eat. I met hedgehogs several times during day time, and I am not worried about them any longer, as long as I can hear a whole concert of their eating noises!