by Kale » Sat May 06, 2023 3:13 am
The majority of shopkeepers that offer an item after speaking to them do so as part of a random event. There is say a 1 in 4 chance that upon exiting their shop completely, the event might trigger. I can't speak for this specific encounter, and there are some oddball implementations elsewhere in the game, but usually you just talk to them, exit completely out, talk to them again, and keep repeating. (Specifically, don't just enter and exit the buy menu; cancel all the way back out and start over from talking to them again)
I think some other events did require buying an item to have a chance at the additional offering, but I’m not 100% sure on this. Notably, Galford required the player to make a 10,000+ gold purchase in a single shopping trip to trigger his stock updating, but that's a pretty uncommon outlier. Try experimenting a bit with exiting completely a few times in a row buying nothing, then exit a few times having bought just one pollen, then exit a few times after making a larger purchase to see if there is possibly a minimum 'gold spent' condition to trigger the event.