Marihuana crisis in Iquitos
So what I found out is that around every month someone arrives with the cargo. Once in Iquitos, it's distributed by a person between the last line of sellers who sell it to the final consumer.
What I have been hearing is that distributor was the one spreading the word of a possible shortage since his guy was supposed to arrive a long time ago, but disappeared without leaving a trace.
So after a month, the time has come: there is no stash in the street, apparently only one place remains that sells it really expensive, and has, just for moments, small quantities.
So travelers beware!
As soon as the tide changes, I shall leave a note advising.