Dave,
Jerry is correct in his response in that in 95% of the circumstances that you described, the ignition switch was left on. However, if both front slides are hydraulic, there are a few components that they will both have in common. If the pump solenoid, the pump motor, or numerous connections have an intermittent issue, it will effect both front slides equally. To properly diagnose the issue, you will need to duplicate the problem and trace the circuit when the slides are inoperative. If you are certain that the switch was off and you want to try a correction without duplicating the problem, the only thing that is economically reasonable to do is replace the pump solenoid and/or clean and tighten the solenoid and pump motor connections.
Gerald