Hawking radiation is only theoretical. It has not been directly observed, and most likely never will be. The release of Hawking radiation deals in very small amounts of energy, while the area surrounding a black hole is generally extremely high in energy due to hot gas being pulled in. The Hawking radiation is much too hard to distinguish from the high energy processes normal at the event horizon, and therefore impossible to detect and prove.
The theory of Hawking radiation combines the black hole mechanics of relativity with the particle theories of quantum mechanics. These two theories are not compatible and can rarely be made to fit together. The fact that two major theories do not work together demonstrates that one or both theories contain flaws, and are not representative of the true nature of the Universe. Because Hawking radiation is an unproven theory based on two likely flawed theories, it is doubtful that it is accurate.