I talked to the Dist. of Mission and their forestry people did not know why the gate would have that sign, especially because it was hand written. They thought that it might be someone trying to protect their favorite camping/fishing spot but not sure. There head guy is going to ckeck it out next time he's up there.
Although someone else told me that the loggers themselves write the signs and they DO lock the gates when they are done regardless if anyone is locked in or not. No cell phone service and a 15K hike back. Not sure that would be much fun.