Erm, no. That is just asking for trouble in my household.
That being said when I was only starting out I'd left it on the bathroom floor and my mum found it. I was naive enough at the time to not think much of it but looking back I think she knew exactly what it was. All she ever said was "if ever you're going to cough up your phlegm again, wash it down, will you?".
I haven't a doubt in my mind now that she knew what I'd done that day.