Are some liquids absorbed by the collapsible container? I poured 1-2 inches of hair oil into 1 and it 100% disappeared when I unpacked (6hr flight).

The pressurization of the plane can force the liquids out. Check the surrounding items is they are wet or moist. This is a clear indication of the issue. This is why it is very important to keep these containers in ziplock with the air removed, then in the original case. I am on 2 to 4 flights a week sometimes 6-8 hours in air and have learned that it’s the smallest details that matter most. Had to learn the hard way!