It depends on company's security policies on this.Some companies just give a temporary badge for the day.Others require the visitor to be accompanied by a company's representative for the day.And some companies require the person to sign in, then get their manager's manager on the line to authenticate this person, and the require a coworker and/or HR person to confirm that the person actually works there and that they need to be in this particular building at this place at this time..In latter case, it's just easier to return home and get the badge (unless the badge is in another country).