Hi ramalannie and welcome to our community
I'd examine the source code. Just select the line of text,
then change the view to TrueCode.
My gut is telling me that perhaps the original Heading was
configured to display based on the Topic Title. Thus, you may have
been using a field. You may have later changed that by attempting
to select some text and type what you wanted there.
TrueCode should reveal what is going on.
Cheers... Rick