If you turn to the “first lines” index of many poetry collections, you can find bonus poems the poets probably never intended you to read.
I found this one in Bill Knott’s I Am Flying into Myself:
A short one from The Complete Poems of Emily Dickinson:
And the alphabetical end of Ron Padgett’s Collected Poems:
Update (4/21/2020): Here is a zine I made from a poetry index: