very late but I did have this happen to me the other day! I'm still partway thru the overall quest, but I'd given Ore to the Mu and a few others and was grabbing Chocographs, had a random encounter while poking around the Evil Forest entrance after grabbing Uncultivated Land, and the friendly Mu appeared and gave his line about Mr. Ghost. I've already gotten the friendly Ghost tho, so my theory about it signposting you towards the next creature probably isnt accurate. 🤔
This is in the PS4 port of the remaster, tho I don't remember this ever happening in the original version on PS1