There were some other pieces I ran into like that, I think out of Salzedo’s Tiny Tales. They’re written for lever harp, but in progressively flat keys, for a lever harp tuned in C-flat. For anything with a lot of flats and no lever changes, you should be able to play it in the key a half step higher (D-flat to D, etc.) and read the same page.
Do you use an electronic tuner? One which can shift the frequency? I use a Korg CA-30 which can shift A from 410 Hz to 480 Hz. I had a similar experience to yours, but my “Fairy” turned out to be a friend of my boyfriend’s who can’t resist any electronic gadget and when left unsupervised for a moment with a beer in his hand had discovered my tuner lying about, switched it on and started messing with all the buttons. I found myself trying to tune with A = 410 next time I used it.
There are definitely such things as fairies, but mine tend to appear in the form of large long-haired beer swilling creatures. Sweet natured, but need to be kept away from button-encrusted gadgets.