The text annotation I made that says "Test" using the Evernote editor was actually added after the one I added that says "MBC R&D Ideas". PNGs are definitely re-indexed because the search found the "Test" annotation. It does take a little time (<1 hr), but that is reasonable. The text annotation that says "MBC R&D Ideas" was added about a week ago, but the search is never able to find that phrase or pieces of that phrase.
The notes I am uploading need to be in PNG format because they are handwritten notes. According to this article, Evernote cannot search handwritten text i