No.

Total bullshit, but one of my favorite car-related myths.

Batteries with plastic cases (and who doesn't have a plastic case battery?) aren't affected by sitting in moisture or on concrete, UNLESS there is battery acid or some other electrolyte on the case which can then make a slow leakage path to ground. Basically, there has to be something conductive on the outside of the battery for there to be a leakage path. Clean batteries aren't affected in the least.

This myth came about from the really old rubber case batteries, the case was slightly porous and there was some carbon content in the rubber, so they would have a slight discharge path to ground if the concrete was moist.

Back on topic, you probably just forgot to hook something back up, or you've unintentionally loosened a connection while things were getting moved around. I'm sure it's something really simple.