In Report View, next to the standard Search Fields on Top, every Column has its own Search Field.
These fields only search/filter in the data set that is visible (per the 20/100/500 toggles at the bottom of the view).
One would expect that a search in a specific column is done through the entire dataset in that column, and not limited to the displayed rows in the view.
Furthermore, oftentimes these toggles are out of sight, and one can easily overlook this extra set of filters that are being applied to the data.