The store would be to blame if it had known that the floor was wet and had not taken steps to remedy the issue. This could mean that there was no sign put on the floor to indicate that it was wet or that there was no effort made to clean a previous spill. As you have the right to be in that location as an invitee, the store owner would have the duty to make sure that you are safe. If that duty is violated, the property owner is liable for damages.