In a fracking context the object that will ultimately block a passage in an isolation device is introduced into the zone with the bottom hole assembly. The object is not released until the guns fire to create a pressure spike in the borehole that triggers the object retaining device to release the object. The retaining device is placed in close proximity to the isolation device and its setting tool to allow a larger object and passage in the isolation device to be used. If the guns misfire, the object is not released and comes out with the guns. The replacement guns can be pumped in because the passage in the isolation device has stayed open during the misfire. Direct and indirect object release in response to pressure created from the firing of the guns is contemplated.