Lightnin' Hopkins did indeed record a live album called "In New York" in 1970, and it has been reissued as a CD on the Candid label, #79070, in 2000. There is a song on that album called MIGHTY CRAZY. (I found this info at AMG - here.)

Barnes&Noble has a sound sample:

Sister got it rub-(?). Mama got it too.
They goin' aroun' doin' the rub-de-rub.
Ain't it crazy? Now, ain't it crazy?
You know it's crazy to keep on rubbin' at that—.

It also appears on two other Hopkins albums: "Blues Masters: The Very Best of Lightnin' Hopkins" (Rhino CD 79860, 2000) and "Take It Easy" (Past Perfect CD 220377, 2002).

Don't know why you couldn't find it. Did you forget his name was spelled "Lightnin' " and not "Lightning"? Spelling can be crucial when doing searches.