I don't think he saw a paper invitation: I think Tess told him.  I think the quote means in the sense of finding the information he needed.  He wouldn't have needed to know much more than that there was an invitation - for instance, Tess mentioning that her employer had been invited to John Watson, the blogger's wedding, or Sherlock Holmes' partner's wedding, something like that.  From there, it would be easy enough to find the date and the venue.  (Although maybe she told him that too!  But she wouldn't need to). 

Last edited by Liberty (January 19, 2018 10:53 am)