Did you use water-based poly? Maybe it's just condensation. Where in the house is this happening? By the bathroom? Near a heating vent? Plez say more. I'm betting that it may seem oily but it's not. I've never hear of this BUT sweating is a possibility.
For now, just keep wiping it up. What you can do as an experiment is lay some Handi Wrap on the floor and see if the condensation/moisture/whatever forms on TOP of the plastic. If it does, well, we all know that water won't seep up, and through, the Handi Wrap. At least not over a day or so ... Let me know how it goes.