Thief on Sash, how will that turn out?

Question

Say I use their w/ a Pokemon that has no item on a Pokemon w/ a Focus sash, Do I take the sash and KO Them?
Do I activate the sash then take it? (Such glitch ;0;)
Or Do I simply activate and break the sash?

Answer 1

If the target's consumable held item is triggered by Thief, such as a Colbur Berry or Focus Sash, it will not be stolen.

http://bulbapedia.bulbagarden.net/wiki/Thief_(move)