If your search is
001 .jpg
& you're seeing "001.jpg" & also seeing the ("unwanted") file "001 blablah.jpg", that means that the file, "001 blablah.jpg", is also duplicated - somewhere.
If you do a search for "001 blablah.jpg" - with no filtering, you should see that it exists - more then once.
And your search (as per above) does match it & it is a dupe, so it is listed.
In my experience it's restrictable to a folder
That is not the case.
If it has happened that way for you in the past, it is only by chance that your earlier searches did not turn up "unwanted" dupes.