Right now it sounds like you do want too much. You have to clue us into why you can't do it yourself, and why it is more convenient for your friend to do these things for you. The only positive is I learned a new word.

Your violin, your responsibility. Make arrangements with your friend for you to pick up the violin, limiting Friend's action to answering the door when you get there. And, honestly, I think you need to rethink whether they meet the definition of "friend", because to me they do not sound very much like a friend. They sound petty and narcisissistic.

You ought to physically assault your friend and inflict injury to get your instrument back. Sometimes, violins IS the answer.

Is there a reason you can't pick up your own violin? I don't blame your friend for being annoyed.

As my father always said, “Don’t lend what you can’t afford to lose.”. That advice has saved me plenty of heartache over the years.

Why can't you get it yourself?