Well it should be there, but your best bet is to download the Dalekeeper editor and use that to add the badge to your inventory. It isn't cheating if you did kill the Giant but simply didn't pick up the badge.
Should be available from Ironworks, but if not I'll post a link to wherever it resides. Off to check now
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Holy Avenger of the OHF and part time Pinguindiebjäger