I don't work for the site, but it's very common for search functions to ignore or eliminate search strings of data when they are very small.
It taxes the server excessively to search for a common one letter word. People with bad intentions could flood the site searches of this type and cause the site to crash.
As Yoc has stated, using less words will find the title you want.
It will also return the results faster.
The engineering software at my work gives a warning if a search is less than 5 characters long and it's the same software that is used by SpaceX to design rockets.
It is always better to use as few search words as necessary to find the title you want. Leaving off common words like "The", "A", or "I" is a good practice.