Just now I was working on a fancy search and replace regular expression.
It looked good so I tested it on one entry then went to the editing area and the search and replace box went away.
I reopened the search and replace box to continue, but the selected text in the edit window replaced my search expression.
Control Z in the search box did not go back to my regex but undid the last change in the editing area.
I can't seem to find a way to get back to previous regexes in the find box. Is there any way? Googling turned up nothing.
Currently, Adobe Brackets doesn't maintain any kind of history of search and replace expressions. The feature is still missing.