if you're on probation you shouldn't be toking. don't know about your area but everyplace else i've heard about people being on probation are watched when giving up their sample. but the best way i've found keeping a substitute warm is storing it in a rubber then tie off and tape to inner thigh. hide a paper clip or safety pin to puncture when needed and go as usual...but like i said, they usually watch and i urge you to think twice about trying to beat them at their game...they've been playing it far longer. should you decide to go thru with this i suggest lots of practice to get it down...even maybe ask a friend to help as an extra pair of eyes to offer any suggestions from the viewer's side...

good luck