You mean "when I read the part where the FBI agents stopped to have a drink I thought"?
This part makes your comment super confusing. Where you there then or later?
Alternatively, they are themselves Ross Ulbricht, describing an out-of-body fever dream or post-traumatic flashback. This seems ... somewhat less likely.
The interlude during which some pushed for "they" to be exclusively plural, was a mere brief blip in the history of the language.
It's also a couple of centuries older than singular "you", so if you want to complain about a pronoun changing between singular and plural, that's a better candidate.
Here it's clear the word is referring to a singular stranger.
They might just be illiterate.
Let’s all be charitable.
Many of us here have spoken English since birth and correctly used "they" in the manner above for several decades.
> Then Ulbricht walked into the public library and sat down at the table directly in front of me, and suddenly as I was reading I could look up and see exactly the chair he had been in, where the plainclothes police had positioned themselves, how they had arranged a distraction.
Alternately:
> Ulbricht had walked into the public library
gives the game away.
If you still want to play around a bit:
> I could see where Ulbricht walked into the public library. The table he sat at. I looked up and saw where the plainclothes police had positioned themselves, how they had arranged a distraction.
That way you are leaving some ambiguity, but are not directly lying with the tenses.
To go into the meat of this: he is imagining it while reading in the same location as the incident happened. This is a style of writing. It's definitely not wrong.
I was willing to give you the benefit of the doubt, somebody who aspires to be a better writer. But, no, this clarifies that you're just pretentious.
Many of us can't. Personally, for nearly three decades I thought the ability to vividly experience a book this way was just some overused and extremely exaggerated metaphor - and then I discovered aphantasia is a thing, and I score close to top of its severity scale.
So perhaps it's less about your starting point, and more about describing a frame of mind some in the audience don't have, and can't relate to.
Curiously, I don't recall ever seeing this particular style of writing before, in any of the books I ever read.
How many languages do you speak? A large part of this site speaks at least two, and usually English is not the first one of them.