You could store the current positions from the geometry you want to look up in a temporary attribute, change the pointpositions, look-it-up, and use the temporary attribute to retrieve the original positions.
But for feeding nodes like "get closest location" it's essential to have geometry context (purple). that's where i need it.
i also tried this (with NO luck):
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there's a SDK example regarding Custom ICE nodes called: "PointGeneratorFromGeometry" which is basically the opposite...