LB, afikomen must be eaten by halachic midnight. If the piece hidden away is not available (e.g. kid who hid it fell asleep and no one else can find it, or kid drives too hard a bargain), or not enough to cover everyone’s minimal shiur, then any matza can be used for tzafon.
Eating matza is a very important part of the seder. One should not fill oneself up during shulchan aruch so as to have room for the afikomen.
I never understood all the emphasis on cooking fancy foods for shulchan aruch- who is hungry after all that matza and who can eat a big meal so late at night?
And by the way, if anything (hand) shumar matza gets more expensive every year. That’s why it is called lechem oni, because it makes you poor. (sorry, old joke)