It would be nice to know what codes were set, but since you disconnected the battery the codes are gone, at least for now.
Light can come on and then go off if the problem corrects itself.
Light could have come on from one of the monitors (checking program that doesn't run all the time such as the fuel evap monitor or the cat effeciency monitor) and either it hasn't been run long enough to set again or it has corrected itself.
