Popa: I did it too. Do you remember whether you said v’achar kein or v’achrei chein?
always runs with scissors fast: No, it’s a halacha brought in RaMBa”M and shulchan aruch. RaMBaM recommends looking over the special prayers before yomtov so you can say them. The mechaber, writing after printing gives looking at a siddur as a second option in general.