Trozzle, read the sentence. It was a joke about mealworms. Obviously sugarcubes are a classic way to dose LSD.
I am reading popped popcorn has a shelf-life of a couple of weeks. Even if you account for the 'Best Before police' being overcautious babies that doesn't sound nearly long enough to be a viable option. Unpopped popcorn kernels can absorb water if you soak them in it (been there done that, for mushroom cultivation), but I have doubts about the shell being permeable to a drop of acid solution. Also if you use water in your acid solution this could cause the endospores in corn kernels to germinate.
My rolling paper suggestion might seem a bit suspicious, especially in capsules, and without capsules it seems messy to store (though you could crumble each one up into a ball and fill a mini mason jar with it and added desiccant pack. Seal and store under proper conditions. Alternatively blank blotting paper could be used if you can figure out a way to put drops of acid on it with enough spacing so that doses are kept separate, but still track where each drop is. You could use a pencil and draw a shitload of smurfs on the blotting paper and dose each smurf.

Then hide it between some drawings from your little sister (not at her place obviously!).
If sugar cubes aren't discreet I get it, but if you worry about moisture breaking down cubes then that is a poor argument since the same objection goes for rice which would spoil.
Like Xorkoth said (and me as well): rice seems too small to get it to absorb a drop without spilling and then dry it out properly, it would get very messy.
By all means reject all our alternative suggestions, but don't stick to ideas that come with unsolved problems simply because you cannot let go if it.
