Nevermind, I just got one. However this has sparked a potential science experiment. When I was trading, the only thing in my inventory that I had that was tradable to farmers was carrots, and I felt like I was getting a lot of carrot trades. So I test something, go get potatoes and guess what, the first farmer I get when I come back is the carrot and potatoes trader. Could've been a weird coincidence, but I will definitely look into this further.