There is a search bar at the top of the file manager that allows users to search any particular folder for any file by name, tag or author (see the area highlighted in red in the screenshot below).
Just start typing the name of the file and it will automatically appear - you don't have to type in the full name, just the first few letters should be enough.
Advanced search:
Next to the search bar on the far right of the file manager, there is an 'Add filter' button. Clicking on this will provide you with the advanced options you can see in the screen shot below.
Search all folders:
Clicking this check box will instruct the search to look across all the folders you have access to rather than just the folder you are currently browsing.
Filter by judgement:
The option to filter by judged and un-judged work.
Filter by comment:
Expanding this bar will allow you to filter by uncommented or commented work.
Filter by hand in status:
Clicking on this bar will allow you to filter files by handed in or not handed in status.
Search by program:
Simply type the name of a program in Purple Mash (2Go, 2Code etc) and any files in that folder that have been created in that program will be shown.