From time to time. playscripts do go out of print in which case the search will not be recognised. It may, however, be possible to find the play in the "out-of-print" section. It may also be possible that a play will be reprinted in the future so it's always worth checking. I do try to keep the listing as accurate as possible but the sheer number of plays in print means that the information given can sometimes not be as up-to-date as I would wish.