I would not be surprised for him not to feel at home after only one day. Leave him alone for a week or 2 without unnecessary handling or disturbing him and he should settle into spending the daytime inside his hide as long as the temps are right and the hide is suitable. A plastic bowl from a dollar store with a door cut in it or a flower pot with an entrance would make a better hide than cardboard. Also make sure that he can't come into contact with the heat lamp (which may well be unnecessary unless your home is really cold).