Sub floor waterway

Any thoughts on the following … Basement with a concrete floor. No moisture issues in home. Owner installs laminate flooring on 3/4 of the floor surface. One small closet is left without flooring. Immediately, the closet becomes damp. Boxes on floor become actually wet. Closet on the main floor above becomes damp and mouldy. My only thought is that when he sealed off the floor (with laminate), the water began migrating to the area where the water was still able to evaporate and created a suction for more water. So the unfinished floor in the closet effectively became a pump for the water in the rest of the basement floor. House is 10 years old. Contractor is horrible. The worst. My guess is if we were to break out a section of floor, we might find no moisture barrier. House is on sand and fill, and lot slopes away in all directions. I don’t suspect any pooling next to the foundation. One other larger area of floor was left untouched, and I think it is a large enough area that the water dissipates into the air without being noticed as it is in the closet. I did not inspect this house. Owner is client of mine as I inspected another property for him. I agreed to help him solve mystery, as he is planning on selling this house and wants to do so in good faith. I’m looking for confirmation of my theory, or any other theories or thoughts that might point to a plan of action. Thanks everyone … sorry for the lengthy description.

Is there a plastic underlayment beneath the laminate? (If not the laminate was put in wrong.)

Was there a recent rain issue in conjunction with the dampness in the closet? I can’t imagine how the closet became a pump. How long was the house owned? How long occupied? Many basements have water intrusion issues. I doubt the flooring has anything to do with it. Look around for other evidence of water intrusion. Stains on sheetrock, baseboards, efflorescence on concrete, etc.

Observe the basement before and after rain events.

Does this home have a sump pump? if not the closet would be a good place to install one. A fairly good test to see if you will have moisture issues after installation of floor covering in a basement is to tape a 10’x10’ piece of clear plastic down on the floor to be covered, and watch for condensation to build up under the plastic for the next week, the laminate floor would simulate this same test on a larger and more expensive level, but if there are no other moisture issues, I wouldn’t expect the flooring to wick water up through a previously dry substrate. At Least not as much as you stated.

Is the part of the basement that is finished heated?