FAT Sorter works at file system level and makes a difference in folder mode only. If the files already are in alphabetically order it has no effect.
I would say the extended functionality of the database mode (e.g. Podcast view) makes it the preferred choice most of the time but the simplicity of the folder view has it strenghts too. In this case, using folder view would certainly be a workaround but as you have noticed there is no resume functionality.
I have tested some sample files on the Sport with the file names 41.mp3, 42.mp3, 43.mp3, 44.mp3, 45.mp3 and 46.mp3. ID3 tags: Genre = Podcast, Album = RollPlay, Artist = RollPlay, Title = same as filename, without .mp3.
They are all listed in the correct order. If your player runs firmware 1.22 (the original firmware lacks track number sorting using ID3 tags) and adding track numbers to the ID3 tag as suggested earlier (use version ID3v2.3) makes no difference, would it be possible for you to put a few files with the problem on dropbox and post a link so we can look at them?
In many ways this issue reminds of this one. Unfortunately a solution was not found:
