With the remote in a closed drawer seems impossible for it to turn on the pre-amp. As already suggested above I would put tape over the sensor on the pre to ensure its not another remote.
Oddly I have several appliances that occasionally "reset" themselves or turn on if off. They do this in unison! Took me a while to figure it out but what was happening is a small voltage dip and then a slight overshoot which caused them switch on. I doubt this is of any help to your sitch.
Regards,
barts