able to see events after deleting

Hi All, We have multisite clustered environment with 24 indexers and 8 search heads and all servers are running with 6.5.2 version. We are deleting some of the events from Search Head GUI using delete command. But in the next day, we are able to see the events with the same query from GUI. Is there any reason why I am able to see the logs even after deleting from GUI? Thanks in advance.