freeMemory() function from memoryfree library not returning decreased value in arduino UNO
You are assuming that, just because you created a variable, it will be stored in memory. That is often not the case.

The compiler is reasonably intelligent. And there are lots of CPU registers in the AVR core. If there is a free register available for a temporary local variable like that, why would it waste time and effort putting it into memory when it can just keep it in a register?

Also, since you don't really do anything with the variable, chances are the compiler is just throwing it away.

Marking a variable volatile will remove both those problems, and you may see different results.