Sounds like a golden opportunity to practise aikido in its most difficult form, i.e. verbal aikido I recommend Terry Dobson's book aikido in everyday living for ideas.
If you are having trouble putting a technique on, ask the person for feed back, what did it feel like or what you are doing wrong ? It doesn't matter what grade you ask, as even a novice might be able to give you an insight into what the problem is.
All I'll say about the Sensei thing is that any sensei worth his salt would do the opposite, and encourage their students to learn from different instructors.
Re the "lesson" with the girl, I interpreted that paragraph as that you deliberately did the pin to teach the girl a lesson. Even though you did the techniques without malice it indicates perhaps some level of arrogance. Of course it maybe just the way you have written it as English is not your native language. Something maybe (or maybe not) to think about.