Still pretty sure Jet was forgotten about after Myron's death, the stables still had lots of other drugs to sell so its not like it was a huge loss.
Jet wasn't forgotten just Myron. Your remembering his ending incorrectly.
but it still does not explain why its in unexplored prewar buildings
Mistakes in placement of random loot tables. Jet is a very minor detail so there wouldn't be someone paying attention to where its croping up.
Jet does survive Myron's death but the people working on it were working for Myron. I doubt he would have given them the full story. They would still be under the control of a powerful mob family. So the odds of someone knowing the full story and getting a way from the family are small and then for that person to make it to DC. Plus the Mordino family would do anything to keep that person there, like giving them, money women and drugs.
The Mordino family disolved and was absorbed by the other famlies, thus the knowledge of jet would be scattered to the four winds. People go on and on about how Myron's genius and claim couldn't be duplicated but one doctor figured out a cure rather easily. Given that a single doctor from vault city was able to develop a cure so quickly once he had a sample. reverse engineering how its made isn't far fetched.
After Myron dies they would still be able to make it. We see it in New Vegas. The effects are different then they are in Fallout 2. I like to think that those that took Myron's place were not able to make it the right way so it isn't as effective. I know it can also be put down to game mechanics. The main point is the chance of DC having the right pre-war protien to make jet is next to nothing.
Well if the effects are different then it could be a different drug simply called jet because of the resemblence. (in which case it doesn't matter if its in DC).
If it is the same drug(and simply a mechanical change) Then as I said, long term production of jet would
require duplicating the cheap protein extract, the extract would need to be much more common or they ran out of the protein extract and had to figure out another method of production.
People being addicted to it, because it is highly addicive is what makes it profitable. It is what hooked the workers of Redding. With a cure out there the profitability and power that comes from producing jet is gone. Which would means those that know how to make it would move on to other things. So people still making it for it to show up in New Vegas could be making it wrong. Another reason why Jet has little effect in New Vegas.
Addiction adds to profitability but its not the only factor. Potato chips aren't actually addictive but people eat them anyway for the pleasure they get out of eating it. Jet would be no different if it provides enjoyment people will buy it. As you said yourself there still making it in vegas so its still profitable, just not as profitable.