[Crannogman]

The stock game includes a Japanese fleet & escort carrier group with a few cruisers and some tankers that departs Taiwan in mid Dec '41, passes down the East coast of Philippines, then transits the Celebes Sea, Makassar Strait, and Java Sea before arriving Sarawak shortly after New Year's Day. This battle group enters the Celebes Sea north of Sangir Island, approaching from either side of Karekelong Island. It stays well north of Sulawesi until entering the Makassar Strait. My guess is that this the group you encountered, but that it was actually paralleling your course to the north.