“If you can smile when things go wrong, then you have someone in mind to blame” is a jocular saying that has been printed on posters. “The man who can smile when things go wrong has probably just thought of somebody he can blame it on” was cited in print on April 10, 1963, in the column “Senator Soaper Says.” The “Soaper” column was written in the 1960s by Bill Vaughan (1915-1977). The jocular saying has been included in many books of one-liners, usually without credit to any source.
 
 
Wikipedia: William E. Vaughan
William E. (“Bill”) Vaughan (October 8, 1915 – February 25, 1977) was an American columnist and author. Born in Saint Louis, Missouri, he wrote a syndicated column for the Kansas City Star from 1946 until his death in 1977. He was published in Reader’s Digest and Better Homes and Gardens under the pseudonym Burton Hillis. He attended Washington University in St. Louis.

His folksy aphorisms (published in his “Starbeams” feature) are often collected in books and on Internet sites.
       
10 April 1963, Redlands (CA) Daily Facts, “The Newsreel,” pg. 16, col. 1:
The man who can smile when things go wrong has probably just thought of somebody he can blame it on.
 
10 April 1963, The Salt Lake Tribune (Salt Lake City, UT), “Soaper Says,” pg. 18, col. 6:
The man who can smile when things go wrong has probably just thought of somebody he can blame it on.
 
Google News Archive
15 October 1965, Windsor (Ontario) Star, “Sheinwold On Bridge” by Alfred Sheinwold, pg. 43, col. 1:
The man who can smile when things go wrong is a bridge player who is about to blame his partner.
 
9 November 1977, Register-Republic (Rockford, IL), “It all proves there is no way to win” by Jim Bishop, pg. A6, col. 6:
“The executive who can smile when things go wrong is about to blame it on somebody else.”
(From Murphy’s Law And Other Reasons Why Things Go Wrong! by Arthur Bloch—ed.)
 
Google Books
The Laughter Prescription:
The tools of humor and how to use them
By Laurence J Peter and Bill Dana
New York, NY: Ballantine Books
1982
Pg. 143:
A man who can smile when things go wrong has found someone to blame it on.
 
Google Books
20,000 Quips & Quotes
By Evan Esar
New York, NY: Barnes & Noble Books
1995, ©1968
Pg. 82:
The man who can smile when things go wrong has probably just thought of someone he can blame it on.
 
Google Books
1,003 Great Things to Smile About
By Lisa Birnbach, Ann Hodgman and Patricia Marx
Kansas City, MO: Andrews McMeel Pub.
2004
Pg. 309:
“If you can smile when things go wrong, you have someone in mind to blame.” (Anonymous)