The search box at the top of the Attachments table will search the attachment's name and the description but will not search the contents of the files. Keep in mind that if you attached a file to your page and deleted it on the page, it will still appear in the Attachments table unless you deleted it there too.
To search for a file, enter a query in the search box, and the results will automatically filter.
You also have the ability to sort by File, Last Modified, Size, and Added by by clicking on the column name. The Attachments table is configured to allow for continuous scrolling to access attachments that aren't listed on the screen.
You can attach a maximum of 1,000 files to a single page with a maximum file size of 268 MB for each attached file.