You can separate the hat from the plane with Poser's Grouping tool. Select all the parts that belongs to the hat (probably easiest to do with the front camera and wireframe view) Then, with the hat seected (it lights up red), click the Spawn Props button and you'll have a new object in your scene. Delete the one with the plane and save the other one to your props palette/library :)

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You just can't put the words "Poserites" and "happy" in the same sentence - didn't you know that? LaurieA
  Using Poser since 2002. Currently at Version 11.1 - Win 10.