...wanted. Gotcha!

Seriously, I asked years ago, and I'm going to try again: does anyone know the name of a sci-fi short story that goes like this:

Time travel is invented, but it can only snatch someone from the future and bring him BACK to the present. So this is done, and a single man is brought back in time. A huge meeting of world leaders and dignitaries is invoked, like a big UN meeting. The man is questioned on various things.

The man says they have cured disease -- but he doesn't know the details. They have this and that gadget that do absolutely wonderful and magical things by our standards -- but he doesn't understand at all how they work.

In the end, we get nothing from this future man, not enough to advance our technology or knowledge forward *one iota*.
Because, the moral of the story is: technology is a huge edifice, a structure, that no one person owns or understands. And it's possible to *live in* and *enjoy* an advanced technological society without understanding even 1% of it.

Star Trek had an episode where people lived with and served by their AI for so long that they forgot how it worked & how to fix it, and how to live without it when it malfunctions.