Hello All: Keith Martin here whistling from Paducah, Kentucky. I am the guy who currently has the mysterious whistle. Another question: Does anyone know where I can get my hands on some slow, haunting Low Whistle tunes? Thanking you in advance… 
If you mean CDs, here’s a good place to start: http://chiffboard.mati.ca/viewtopic.php?t=18801&highlight=low+whistle+cds
Ireland’s Best Slow Airs.
Includes music and two CD’s. There are some reeeeaaaaallllllyyyyy slow ones in there.
Hi Keith
Gorgeous whistle - did you make it?
You might want to check out http://www.thewhistleshop.com. They have a nice selection of books and CDs - and the owner, Thom Larson, is great. Another website with sheetmusic and some mp3’s is http://www.tinwhistler.com/music
Happy hunting!
~Judy
Try playing some of your old favorite faster tunes (reels, jigs), but at a slower pace. They take on a whole different feel on the low whistle.
Another book which I believe is different from the one NorCal mentioned: Traditional Slow Airs of Ireland, ed. by Tomas O Canainn, available with cd. A veritable cornucopia of beautiful slow airs. There’s also a few slow airs in The Low Whistle Book (by Steafan Hannigan & David Ledsam), including the famed Lonesome Boatman (2 versions, actually). Otherwise, I just try to keep on the lookout for any slow airs, laments, songs and all manner of melancholia wherever I find it. Except requiems for recorder. or anything by Celine Dion. and there’s a certain fellow who was once the piper with Moving Hearts that plays a haunting tune or two…
p.s. tinwhistletunes.com also has a section with slow airs:
http://tinwhistletunes.com/clipssnip/slowairs.html