This is probably what I'd do if (as Shane inquires) the folder contents is relatively static.
Creating a text file with all the folders in my home folder gives me a 15.5 MB file with about 97,000 lines.
This script using the Satimage.osax will search it in ~ 0.7 seconds on my system – even faster if I turn ON case-sensitive.
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set folderDatabase to alias ((path to downloads folder as text) & "FindResult.txt")
set foundItems to fnd("^.+Folder_01$", folderDatabase, true, true) of me
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--» HANDLERS
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on fnd(_find, _data, _all, strRslt)
try
find text _find in _data all occurrences _all string result strRslt with regexp without case sensitive
on error
return false
end try
end fnd
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