Possible to FAYT within filenames?

Yes, exactly. Filters are awesome, and I love them. They are very powerful and have their uses, but they aren't really the most efficient way to find a single file. FAYT is very good at doing this quickly, and easily, but currently it only searches the beginnings of filenames for the string you've entered (as shown in my screenshot a few posts up).

I think FAYT searching the entire filename for substrings would at the very least be a very useful option.

This has probably reached the point at which you might want to consider submitting a feature request at gpsoft.com.au/Support.html.