ID:2035879
 
Not a bug
BYOND Version:509
Operating System:Windows 10 Pro 64-bit
Web Browser:Chrome 48.0.2564.109
Applies to:Dream Maker
Status: Not a bug

This is not a bug. It may be an incorrect use of syntax or a limitation in the software. For further discussion on the matter, please consult the BYOND forums.
Basically, if you try to ctrl+F something in DM, unless you use Find Next (F3), reopening the find window will not retain the input unless you have it highlighted. It will rather replace the input with something else highlighted, or the word before the blinking cursor.
Lummox JR resolved issue (Not a bug)
I'm gonna say this is a bug, or a usability issue.

If you do a find, and mistype it, and you re-open the find box, it should only replace the contents with what is selected if you actually have something selected. Other wise it should have the old contents so you can edit your typo without having to re-type it.

I've wanted to make a Bug Report on this issue myself many times, it's rather annoying.
I wasn't sure if it was a bug or intentional so I let it be.