I am reminded at this point of a QFI friend who didn't realise for 10 minutes whilst teaching a pre-solo student that he had a stuck PTT. On realising he turned the radio off, landed, and phoned to apologise to a charming lady air trafficker.
QFI - explains, and apologises
ATC - "No problem, I just put all my military traffic over to UHF and ignored the civvies. But, could I just ask you one question".
QFI - "Glad about that, what's the question?"
ATC - "What's this 'bloodyrudder' that you kept telling your student to use"
Absolutely true, I was drinking coffee in the crewroom as he made the call.
G