When searching the results of a previous search, the only visual clue of it being a limited search is that the "Look in" field is blank.
A filename search that results in 75 matches followed by "Search results" (correctly) causes the paths of all the matches to be displayed in the "Look in" field.
However, a similar search with 176 matches followed by "Search results" causes the "Look in" field to be blank. Pressing F5 to rerun the search (on the filtered list) without altering the criteria doesn't change that, see before and after below. So it appears there's some threshold at which the paths are not displayed.
This is a very subtle indication which could lead to wrong conclusions from search results, particularly if the user only changes the File name or containing fields, and (mistakenly) assumes that the original search path was still being used.
Would it be possible to make restricted searches more apparent, eg by colouring the Look in field (say, pale pink) and including a relevant text message (say, previous Result List). Alternatively, to maintain the GUI style, you could include a Result List tab with a red tick, when appropriate.