Is using a thermal camera an effective method to locate mold & moisture behind finished walls in a basement?
I doubt it. I'd assume that any water which has made its way far enough into your house, to wet the backside of drywall, would have already acclimated. It's hard enough to find gaping holes in the exterior of a building by scanning a panel of drywall. 

Thermal cameras are used to find heat gain, standing inside, or heat loss, standing outside. Suggested reading: Where do I need to drain the footing drain when I waterproof a basement from the outside? You need to somehow drain or shed rain water away from the house. See any cracks in the foundation?