retrolefty:
Servos are not designed to be powered up but with no control system, so the manufacture will not give you a behavior in that state, so you can only test to see what happens. Also you need to make sure the arduino servo output pin is set to LOW output so current won't try and flow to the servo when it's powered off. And most likely a jitter will happen when you attempt to re-power and re-attach.
I am also making one of these reverse geocache boxes and using a servo (TowerPro SG-90) as a locking pin driver.
I currently have the servo power supplied from a main 5V power bus (off the VCC pin of my Sparkfun Pro Micro). When the whole box is powered up, currently, the servo gets power too.
My issue is that the servo jitters when power is supplied, enough so that the locking pin becomes momentarily 'unlocked' ... kind of defeating the point. I've tried delaying the 'attach'ment of the servo, or immediately giving it a location to go to, or trying to manually set the signal pin low or high .... no luck.
Is my only option to put in a relay or transistor and only power the servo when I absolutely need it to move?