Java Edition Alpha v1.0.1 Redstone wire has an extra, unobtainable item form corresponding to its block ID. It can be obtained via inventory editors with numeric item ID 55.
Unlike the obtainable redstone dust item, this unobtainable form can replace blocks such as water.
Java Edition Beta
1.6 Test Build 3 Redstone wire items can be obtained from the newly added debug chests, mainly from the 24th slot of the 2nd chest from the left, and the 8th slot of the 6th chest from the left.
release Debug chests no longer spawn, preventing redstone wire items from being obtained this way.
1.8 Pre-release 2 ;) Added pick block functionality. This will change the currently selected slot to any containing this otherwise-unobtainable redstone dust item, but will not allow it to be obtained if not already in the hotbar.
1.2.5 pre Pick Block now returns the actually obtainable redstone dust item.
1.3.1 12w15a Redstone wire items can now be obtained via Pick Block in creative. 12w16a Pick Block once again returns the actually obtainable redstone dust item.
Redstone wire items can now be obtained in singleplayer worlds via the
/ command using the respective numeric ID.
1.7.2 13w37a The direct item form of redstone wire has been removed from the game. It can no longer exist as an item in any way, only as a placed block.
Pocket Edition Alpha
? Redstone wire can exist as an item.
Legacy Console Edition
? Redstone wire exists as an item. 
Appearances [ ]
This section is missing information about
Please expand the section to include this information. Further details may exist on the
Java Edition Alpha
v1.0.1 The redstone wire item uses this texture in inventories, when held in first person view or as a dropped item.
? The redstone wire item uses the aforementioned texture when held in third person.
Java Edition Beta 1.3 The redstone wire item now uses this texture in inventories, when held in first or third person view or as a dropped item.
This is due to the redstone wire texture changing in this version to use tints.
1.4.2 12w34a The redstone wire item now uses the aforementioned texture when in an item frame.
? Redstone wire looks like this in the inventory.
Legacy Console Edition
? Redstone wire looks like this as an item. 
Names [ ]
Item names did not exist prior to Beta 1.0.
Beta 1.0 - 13w36b: Redstone Dust
References [ ]