Hi Deepak,
be aware that Exists is the property of an "existing" object.
According to how you get your ObjectToFind, it could be a stub object with an Exist property that is false, or it could be null.
Window(aName) will return null if the window doesn't exist (and add a log ), where waitWindow will return an object with Exist = false and will not add log.
I guess you've used the first method and the Log entry come from this instruction.
See
http://support.smartbear.com/viewarticle/30939/(the behavior is the same with other objects)
Christophe