So does the latest modpack (7.3.0) somehow reduce the chances of finding the Swamp Lotus in a random encounter? Because I've been through FAR MORE encounters than I've ever had to do before since accepting the quest (last time I played I was using 6.0.0), and I haven't found the bloody thing yet despite having had a great many swamp (black water, black trees) encounters. Once upon a time I used to be able to find the flower by simply saving the game before leaving Hommlet, and re-playing the trip to the Moathouse until I'd found it. That's not working any more.
I, on the other hand, found it on the second RE after accepting the quest, which is quite a bit faster than usual. Random encounters are random *shrug*. FYI, there are 2 different swamp RE maps, and it only shows up on one of them. You must've been getting the other one.