I think when you unplugged your car battery, it could have reset your player. Normally the player is wired to the car electrics such that it's still using power even when you switch off your car.

When you disconnected the battery, it would have totally cut off power from the player, so lot's of things could have been reset.

I suggest you read the player's manual if you still have it with you. Otherwise, you should go to one of those shops which do all this player wiring and ask them to check it out.