Except I don’t remember any the exact particulars, if it was a cartoon, a line drawing, or a painting. So the description following may be wrong in almost every detail. But the gist of it is that it’s a scene of a virtually empty flat desert except for something like two small rocks and maybe a cactus about a foot high and four inches wide. The scene is titled “three Apaches”.
Just to let you know that you are not going crazy, yes I remember it. Very good gag. Like you I am fuzzy on the details. I thought just a line drawing. I hoped it was Gary Larson but, although he has plenty of cactus cartoons, it wasn’t. Now I am annoyed that I can’t dig it up.
Something like that is mentioned in the book Those who Hunt the Night by Barbara Hambly. Or possibly the first sequel Travelling with the Dead.
Could be a Kliban, maybe?
Thought it was gonna be: “Patience my ass, I’m gonna kill something”
I want one with a pig at a Complaints Department saying “My wife is a slut.”* 
*Seinfeld reference.
Reminds me of this:
