Could it be that your feet were perspiring?

A thousand years ago I was pre-testing a tent/sleeping bag combo I was going to use for motorcycle camping. I hadn't camped but once like that before.

The morning after the 1st night there was water on my sleeping bag and where it had touched the tent. 2nd night I put a garbage bag over the foot of the sleeping bag. Next morning the water was inside the garbage bag. My feet had transpired that much moisture.

Since then my feet have transpired many more gallons of water - especially while hiking.

I hope this info was useful :-)