@Iron_Guard8Well that's just sad. I always thought that upgrade was shaving the prize bulb mountain down. Turns out it was a some sort of hope-induced mirage. Lots of characters can lose that upgrade now since I don't care a bit about GM levels.
Edit - The good news is that with the helpful tips from everyone here I'm feeling better about my chances of finishing the prize map this month. And now I can put in upgrades that are useful on characters that are mastered instead of falsely believing I was getting something out of leaving this upgrade on.
Still haven't seen prize bulb gnome in Giddy Park but I probably just need to visit more and actually reset if I don't get the event I want instead of doing the activities I don't want and waiting it out.