Even though no human, time lord or alien was around at his time of passing, the Doctor did not die alone. By his side at the very end was his oldest and greatest friend, the TARDIS. While his companions came and went, his spaceship had never let him down. Mind you, it was fickle and temperamental more times than it wasn't, but a bond of steel had formed between the two of them. The Doctor's tawdry quirks meshed perfectly with the TARDIS's, from his strange wardrobe and ridiculous hair to its broken chameleon circuit and jammed brakes.
The TARDIS had never given up on the Doctor. While the rest of the world would have forgotten the man when he died, replacing him instead with stories of an impossible hero, the TARDIS remembered, and the TARDIS fought back. Acting on its own free will, the TARDIS turned its knobs and gears, pressed its buttons and levers and battled against time and fate for the sake of the Doctor.
And then, something happened. Across all of creation, every planet, every solar system, every galaxy and universe, a great blue light flashed. For a brief second, all of time and space folded over itself, and the time vortex enveloped everything. As quick as it had expanded, the light of time retracted, focusing its entire energy on one point, wrapping itself around the Doctor.
The vortex retraced the Doctor through his hundreds of years, reliving and remembering his existence. And then, as all of his lives converged into one singular point in time, the Doctor opened his eyes and looked around. Confused, he patted down himself, as if to assure he was actually alive. Two legs, two arms, ten fingers, hopefully ten toes, everything was intact. Feeling safe with his self-assessment, the Doctor looked up at the TARDIS and smiled.
"Ohh… Oh! Brilliant!"