Hoarding supplies while comrades starve?

[Kingfisher]

In a current Hotseat match the allies had captured Lunga, forcing the Japanese to retreat to Tassafaronga. For several weeks the garrison slowly withered away until all that is left is a HQ unit and remnants of 3 regiments. The base hex showed zero supplies and each unit also showed zero supplies.

All made sense until about a week ago when another remnant, this time part of a base force, appeared in the same hex. I am playing both sides and am positive I didn't transport this unit to Lunga. In any event, with the allies having strong air and naval bases at Lunga, Irau and Russell Islands no Japanese transport (or barge) could have survived the trip. What is even weirder is that the base force shows as having over 3,000 supply points on hand while the other units are knawing on tree bark to stay alive.