Note in score grayed out and won't print

I was composing something (using tabulature.) I'm not sure how, but when I printed out my work, one of the notes was missing from the score. I assumed that I accidentally deleted it (one of my pet peeves with this program is that it can be very easy to unintentionally select a note and either edit or delete it) but when I reopened the score, the note was still there but was grayed out, like a ghost. I could not get it to reappear to be printable. When I used the playback feature, the "ghost" note still sounded. Eventually I was able to delete the note and re-input it so it showed up normally again and was able to print... but what just happened?