Your comments

I definitely run into behavior on a regular basis where I have only a few characters selected (all on the same line) and find acts as if 'find in selection' is selected.
When this happens the 'find in selection' button on the status bar is *not* depressed, but the find fails because the search is only happening in the selected region.

I haven't narrowed it down completely, but I *think* it happens with sequences like:
* search for something (which leaves some snippet of text selected)
* switch to another app (e.g. my the browser)
* switch back to sublime and try a search

I don't have a 100% repeatable way to reproduce this, but I run into quite often.

I notice this mostly on Mac, but it may also happen on Linux. I'll try to narrow it down more.
It would be nice to be able to disable this behavior. I also run into it all the time.