The son, Guus, apparently had gone to Soerabaja. He was married to a woman named Guus Mulié, who died a couple of years later in an auto accident. The connection comes from the notice posted in Utrechts volksblad : sociaal-democratisch dagblad of 21-03-1940 by the Ph Sammes family and his sister, Sophia Harpman-Sammes. This may explain why his name doesn't appear on the list of survivors.
Addition
Guus Sammes
Guus Sammes in Soerabaja