Reply To: search for a text in a folder?

You can't use InDesign to scan through a folder. You also can't really rely 100% on an external utility that can scan binary files for text — the text in the file may be broken into several parts, or contain invisible characters such as discretionary hyphens or non-breaking spaces, or even visible characters such as ±, that are stored as Unicode values.

If you really want to find that elusive document, open all in InDesign and do an “All Documents” search.