lo había dormido

22:44 Aug 21, 2021 

That's great! I had seen "knocked out," too. I was hesitant to say so because it felt like it might be assuming too much to think the woman in the email hit the guy so hard she knocked him unconscious. But I really can't tell from what's there what is going on. I think that is not just Argentina but pretty much everywhere. "Dormir a alguien" is either putting someone to sleep, or anesthetizing someone, or knocking them out. Since you are in Argentina, have you ever heard it used to mean "to cheat/trick/fool/deceive"?

22:25 Aug 21, 2021 

An example in Argentine Spanish describing a match won with a goal in extra time. A knock-out blow
"Lo durmió en la última - Oléhttps://www.ole.com.ar › Ascenso
Translate this page
Dec 29, 2020 — Lo durmió en la última. Morón venció al Pincha que no pudo escalar a la cima. Morón metió un triunfazo.

20:36 Aug 21, 2021 

You might be on the right track. But it only mentions Cuba and El Salvador for the transitive verb (which is what we need). And the email is Argentinian Spanish. The meaning listed for Mexico and the Dominican Republic only applies to pronominal (reflexive) verbs, so it can't be that. Still, in Argentina they might use transitive "dormir" to mean "embaucar" and the RAE just didn't list it. They can't be expected to keep up with everything.

20:21 Aug 21, 2021 

the transitive form of "dormir" can mean "cheat/trick/fool/deceive" in some parts of Latin America.
12. tr. Cuba y El Salv. Embaucar a alguien con el fin de obtener algún beneficio.
17. prnl. Méx. y R. Dom. Engañar a alguien, embaucarlo
https://dle.rae.es/dormir?m=form

19:17 Aug 21, 2021 

To me it's not clear if I can't find a single instance of the phrase being used in a similar context after extensive looking. A reference should exist somewhere.

18:45 Aug 21, 2021 

I think the meaning is pretty clear

18:27 Aug 21, 2021 

I looked into this but in all the many instances of the phrase "lo habia dormido," all just had to do with putting someone to sleep. Whether by drugging them, or simply putting a child to bed, or even a body part going numb. "En una oportunidad" didn't seem to alter the meaning (as part of an establshed phrase for instance). It seems to just mean "on one occasion."

Sorry I really couldn't find anything. I think it's very difficult to judge the context from such a short segment of the email, because I don't even immediately see what any of these sentences have to do with one another (they lack cohesive connectors). There seems to be a lot of "inside" knowledge/hidden context there.

The two answers suggested so far both seem plausible but I couldn't find any examples to back them up.