safari "find" does not work for partial word
This is by design. Clicking on the magnifying glass next to your search shows a menu that allows you to switch between Contains and Starts With, with the latter being the default.

There is a hidden setting to change the default to Contains.


Quit Safari. (Safari menu > Quit or Command-Q)
Open Terminal. (Applications > Utilities > Terminal)
Copy/paste the following line exactly and press Return:

defaults write com.apple.Safari FindOnPageMatchesWordStartsOnly -bool FALSE



The next time you run Safari, substring matching (which is what you are trying to do) should work correctly.