Water On floor under bath room sink

[Mark C]

I found water on the floor under the bath room sink. I wiped it up and checked the lines under the sink. I did not find any water on the feed lines or drain lines. The next morning after a taking a shower I noticed water leaking from the shower pan on the floor and going under the sink cabinet. I said I would rechaulk the shower pan when we get home later in the day.
Before leaving the camp site we put a hand towel on the floor under the sink.
When we arrived home the towel was wringing wet. Where did the water come from? The tanks were drained before leaving the site. Once home I opened the red and blue drain lines under the trailer, some water did come out. Help!