Because of the existing inventory history, you can't really get rid of the item. Instead, mark both the Item Site and the Item itself as inactive. The inventory history may be tied indirectly to entries in the general ledger, depending on what activity occurred for the item. Thus you should probably keep these records for auditing purposes, even if the item was created incorrectly.
Out of curiosity, what kind of inventory history exists for an invalid item (Inventory -> Reports -> Inventory History -> by Item...) ?
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