Literature reports of hydrogen absorption by nanostructured carbons range from nothing to tens of weight percent. We studied pristine graphite and two potassium-graphite intercalation compounds (GICs) using muon spin relaxation (哒), because the positive muon is expected to behave like a light hydrogen isotope. The graphite did not trap muons, but at low temperatures a component of the 哒 spectrum from the two GICs could only be modelled by the Kubo-Toyabe function. This result demonstrates that muons were trapped by these samples and implies that H atoms would also be localised in these traps, in qualitative agreement with accepted hydrogen absorption results. Thus 哒 is confirmed to be a valuable probe of the relative ability of carbon-based samples to bind hydrogen atoms.