In mistake for something
Definition 1 of 1
Pro Tip 1/3Usage Clarity
Use 'in mistake for' when clarifying a wrong identification or choice happened. 
She called out to a stranger in mistake for her friend.
Pro Tip 2/3Error Emphasis
Emphasize errors due to similar appearance or qualities between items or people. 
The novice birdwatcher recorded a common thrush in mistake for a rare species.
Pro Tip 3/3Accidental Choice
Highlight accidental selections, not deliberate choices when things look alike. 
He took the diet soda in mistake for the regular one due to identical packaging.