An idiom for a stupid action which is beneficial in the end, or for the person who performed said action

My friend works for an investment firm, and his colleague mistakenly double-submitted a long bid for stock on a very risky day. The entire firm was on edge the whole day, watching the stock price. In the end, the price went sky-high and the firm made a lot of money, so the friend was praised. However, he could easily have been in big trouble with the boss if the price had dropped. What is a term for this? Also, is there a term for the person who made the mistake?

Solution 1:

One expression is 'fall in s--t and come out smelling of roses'. It's fairly common that people use just the end of the phrase: 'come out smelling like a rose', to avoid the vulgarity. This can apply to bad luck or stupidity.

Solution 2:

Dumb Luck: the way in which something good happens completely by chance, without being planned or deserved. (Sometimes emphasized by adding sheer before it: Sheer dumb luck.)

Solution 3:

He lucked out.

luck out: To be a benefactor of good fortune rather than fall victim to circumstance.

Solution 4:

The term for the result of the stupid action could be happy accident, meaning a blunder that ultimately proved advantageous. However, this term is occasionally used as an informal euphemism for "unplanned pregnancy", so use with caution.

An adjective used to describe such blind luck is fortuitous (there is also a noun fortuity). A single instance of blind luck is a stroke of luck.

Although this does not coincide precisely with the concept you are trying to express, the word serendipity means "the luck of finding something pleasant when you do not expect it".