During the genrations, many items have been forgone for other items. Eg- Till Gen IV and in Gen VI Old Rods and Good Rods were available but in Gen V they were unavailable; In Gen III there was a distinction between bikes: the Acro Bike and the Mach Bike but in Gen IV the distinction was removed; Pokeradar was available in Gen IV and is Available in Gen VI but is unavailable in Gen V.
Other Key items like Coin Case and S.S. Ticket were also removed due to the change in the overworld.
It's most likely that there was not time enough to programme and incorporate these items into the storyline, hence they were removed. It is not due to any glitch.
Source - A few trial rounds with the games.