No retcon;
http://www.wowpedia.org/Gnomish_Flying_Machine. Gnomes played a rather important role in WarCraft 2, building flying machines and submarines. However they weren't seen in WarCraft 3 simply because they were unable to support the Alliance as they had to deal with the Trogg invasion. Gnomes are important, in their own odd little way.
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I still don't get why people were expecting High Elves. After TFT it stands clear that only a handful of elves survived and most of them "became" Blood Elves and went to Outland.