@startuml
class foo
note as N1
"This is a floating note"
end note
foo .. N1
@enduml
this does not produce a line to the class as per the UML spec... I would suggest perhaps you have a comment type (as per the spec) and that comment type is a specialization of note.. in that comments are drawn without connections by default... but if a connection is specified then a line is drawn between the comment and that item (in another issue, I also raised the fact that one could not tie a note directly to a relationship which is allow by the standard)