After seeing/hearing conflicting info on rice, I asked a Modern Orthodox rabbi who has worked as a mashgiach (rabbi who certifies kosher food) about it. You are correct that one says the "mezonot" blessing over rice. But after eating rice, you don't say the "brakha acharona" with "al hamichya” as for cake or food made with one of the five grains mentioned in the Torah (wheat, barley, rye, oats, spelt), but rather the shorter "borei nefashot" bracha which is used for foods that are not "hatmotzi" or of grains in the Torah or the Biblical fruits of the land of Israel (grapes, figs, olives, dates of pomegranates) or grape wine.
My understanding is that a food must either be made of one of the five grains of the Torah or cooked rice in order to get the "mezonot" blessing. (note that corn is NOT one of the five grains) So if a cupcake does not have any of those grains, then I think does just get the "shehakol" blessing. (Interesting side note: I just checked a website and found out that since rice cakes are made by steaming rice kernels until they pop, they get the "ha adomah" bracha. This is why my husband tells me that there are "bracha competitions" in Israel like the US has English spelling bees.)
A related situation: A lot of times airplane kosher meals will have a note accompanying a dinner roll explaining how because of its ingredients or size it merits only the "mezonot" blessing, obviously to decrease the number of passengers who would then need to use the restroom to wash their hands before eating the meal.
