Interesting that you say the "snowflake" wheels should be tubed ? when i did my rebuild the tyres i replaced were tubeless and the ones i fitted are, that said i am an occasionall rider and always check the pressures before i set off usually losing 1 to 2 psi a week the longest run i have done was just over 200 miles with no significant loss when i checked them the following day.
As for the sudden loss of pressure does seem strange that you didn't not notice anything before you arrived.
Lou