A list of some Unavailable Items: items that were never released formally or have since been retired from the game. Most were retired as part of the July 28th, 2015 update.
Mill[]
Tree/Crop[]
Resources[]
Wood / Bucket of wood
Stone
Bamboo poles
Marble
Old Bazaar[]
Bamboo chair
Kite
Precious gemstones
Platinum
Flowers
Coins (these items have been returned to the game as tokens used at Wishing Wellspring Island)
Tools[]
(the wheelbarrow has been returned to the game for the Grand Gazebo and Topiary Fountain event)