The Case of the Missing Clue with Perry Mason by Tommy Flach (1959)
Mystery writer Erle Stanley Gardner was used to getting a lot of letters, but one he received in 1958 tickled his fancy. It was from Tommy Flach, a 9-year-old fourth grader at the Nathan C. Schaeffer School in Camp Hill, Pennsylvania. Tommy was evidently a big fan of the Perry Mason television show and, since his grandmother had given him a new pen, he decided to try it out and write his own Perry Mason story. The result -- a fifteen page playlet -- he sent along to the creator of his favorite detective.
Gardner love the story, complete with misspellings and odd jumps here and there. The result was that he sent the "manuscript" to his publisher William Morrow which, in turn, published it as a book priced at one dollar. The book included a facsimile of young Tommy's fifteen-page handwritten manuscript along with a three page introduction by Gardner. The introduction was actually longer than the little play.
To quote Gardner:
"The script is good for a laugh anywhere, and then it is worthy of a sober second reading. Beneath the evidence of immaturity in execution there is a real appreciation of dramatic values, an appraisal of life which is indicative of the rapidly changing times in which we live...There is no limit to what imagination can accomplish once imagination is given free rein and permitted to develop...[R]ead it a second time. I say again -- to my mind this is a very significant document."
Gardner's introduction -- titled The Case of the Boy Who Wrote "The Case of the Missing Clue with Perry Mason" -- was mistakenly credited as the title of the book and the book (further mistakenly) credited to Gardner himself in the St. James Guide to Crime & Mystery Writers. So this is not a missing Perry Mason book, but it is an interesting curiosity.
I won't go into the plot (such as it is), but I will say it involves a brutal death, a missing will, and a surprise ending.
As far as what happened to Tommy Flach your guess is as good as mine. A brief search of the internet (really brief, actually) shows a Thomas C. Flach who lived in Pennsylvania who would be the right age. Wherever and whoever he is, I hope Tommy is enjoying a long and happy life and is secure in the knowledge that he contributed to one of the many interesting side roads of mystery fiction.