You can lose "true" weight during the day, while still gaining enough weight from food/water to offset the previous night's fasting and weight loss.
In other words, it's not that you don't lose weight until you sleep: it's that you can't differentiate whether you have net lost weight or gained weight until you have similar conditions of measurement.
Yes, thank you, this is a better way of describing the process that I observed.
But I would add to this, that it seems that you can lose some net lost weight from not having enough time sleeping for the process to finish.
Maybe like how a sceptic tank gets filled and drained repeatedly, but only gets drained at night (for an equal analogy). And if there's not enough night (sleep), it can't drain completely, therefore retaining waste.
It would explain also why you get sick if you don't get enough sleep... something else to ponder.
In other words, it's not that you don't lose weight until you sleep: it's that you can't differentiate whether you have net lost weight or gained weight until you have similar conditions of measurement.