Mmm, ok, the premise of the story is that a naturally occurring antimatter star collapsed into a mass of neutrons and anti-protons. This this neutron/ anti-proton mass over a period of millions of years slamed into normal matter objects annihilating them an bits of itself until it's reduced to approximately the mass of an M class planet.
Along come a mystery person who creates a pocket universe around the anti-protons sort of like Wesley crusher did with the Enterprise's warp drive (Remember Me). This allows a loop hole in physics. He isn't moving the mass, he is moving the access point to the pocket universe. He places this pocket universe inside multi-purpose cylindrical container equipped with a bale handle (see file BK3T-5). Said person of mystery puts container into storage at a Ferengi self storage facility in the Promellian region.
Weeks later a Cardassian arrives, ans spends several hours in a bar before buying Cardassian porn and retrieving the container. He places the container on the roof of his small budget shuttle while loading the shuttle with his porn and booze and forgets the container.
It is suspected the navigational shields held the container in place until about warp 4.3 to warp 4.6 at which time the container smacked into the shuttles warp pylon causing the anti proton mass to be released from the pocket universe. The shuttle is consumed by the explosion that rips a hole in subspace.
Somewhere several sectors away a junior Federation technician notices the explosion on a long range sensor and says: "This just ain't right. We need a closer look." (insert story involving Breen, Ferengi, an understaffed saber class ship, left overs from the Promellian/ Menthar war, and technobabble here).