Just clicking out of the find box also leaves the user in Find Mode, not browse mode.
I've never been a big fan of using a script for finds that just enters find mode and pauses.
I prefer to set up a group of global fields where the user specifies find criteria while still in Browse mode. A script then enters find mode and uses the data in the global fields to construct find requests and perform the find.
In that scenario, canceling the find is simply a matter of either closing a popover, closing a modal window, or clicking a cancel button that does the same thing.
For examples of scripts that use global fields in this fashion, see: Scripted Find Examples