Eddie,
In cool weather, low humidity, and high winds, I think you could get up to .1" per day of evaporation. It's possible that you could have lost 1.5" or slightly more to evaporation over 3 weeks.
Add that to a little compaction and soakage, and it doesn't sound alarming.
If you didn't run into a lot of sand and gravel during construction, I wouldn't worry.
A reason for the "lag" in sealing is that it takes a while for the water to soak into the soil. As normal soil becomes wet, it becomes heavier and more plastic. The heavier and more plastic it becomes, the more it settles and compacts. The more it compacts, the more waterproof it becomes. In effect, there's an ever-decreasing loss to compaction and soakage. You should know something in a month or so.
