This being more of a set-up for an interactive discussion rather than an actual story i moved this from the fictional story section to Tugs Talk.
As for the situation itself, all in all this strikes me as an unrealistic scenario. Even leaving aside the the question of which anyone would set up this situation and then leave the knife and cell phone there as stated or use a bomb so easy to disarm. If you're tied so tight to a chair heavy enough to make it doubtful you can move 15 feet in four hours, you're not going to have the dexterity to do any of the solutions you have mentioned anyway. So all seem equally pointless to me.
But then i always was something of a literalist.