Temperature difference: If the temperature was significantly colder yesterday than it is today, the antifreeze may have been more likely to leak. This is because cold temperatures can cause seals and gaskets to shrink and become less effective at holding back fluids.
Vehicle movement: If the truck was driven more extensively yesterday than it was today, the increased vibration and movement may have caused a leak to develop.
Coolant system pressure: If the coolant system was under more pressure yesterday (for example, if the engine was running at a higher temperature), it may have been more likely to leak.
Temporary blockage: If the leak was caused by a temporary blockage (for example, a piece of debris that got caught in a seal), it may have cleared itself up by today.
Without knowing more about the specific circumstances of the leak, it's difficult to say definitively why it happened yesterday but not today. However, any of the factors listed above could potentially be responsible.
