Prankster's Return:This could be something that I was doing but despite placing several grenades in peoples pockets the achievement wouldn't unlock. As soon as I found a mine (a Fragmentation mine to be exact) I found a victim and placed it in their pocket, which worked because the achievement unlocked. So if you're experiencing the same issue, perhaps try that out.
To be able to do this you'll need to be at least Level 6 and have a Perception rating of at least 1. You'll also need to have a 2 star rating in the Pickpocket perk (located directly below the Perception rating) as this allows you place a live grenade/mines in a person's inventory.
To do this, find an unsuspecting victim. Go into sneak mode by pushing in the
(Right stick) and sneak up on someone. Be sure that text on screen is green and says "[HIDDEN]". Then pickpocket them and place a grenade or mine. The achievement unlocked for me as soon as the mine had detonated.
Unless you don't care what the NPC's of the game world think of you, it's advisable to save your game before attempting this. Allowing you to unlock the achievement and reload the game as though you didn't just blow an innocent farmer to pieces.