The find file function is in the File Manager. Click on Window --> Files . Right above the file listing is a search box.
That particular search field is only available on Macs.
Windows users don't get that option in their Files window...
...there currently is no function within DW's Find & Replace Tool that can find by file name alone, and then make changes to only those pages. You could highlight the files you want to work with, within the Files window (using Ctrl + Click to highlight multiple files), hit Ctrl + Shif t+ F, then change the Find In to "Selected Files In Site"...
...obviously this is not ideal on medium to large sites, but it's all we have to work with currently.
Make sure to add your voice to other feature requests, or start a new one here:
The DW Files Panel (F8) sorts filenames alphabetically in either ascending ↑ or descending ↓ order. To change sort order, click the Local Files arrow and scroll to the filename.
Alternately, use your operating system's file manager or Adobe Bridge to search for specific files on your hard drive.