I've tried using Musipedia on several different occasions, and achieved absolutely nothing. It lures me with the ‘microphone’ section, into which I tried whistling after jumping browsers to resurrect Flash from the dead. I've clumsily transcribed a couple melodies into the ‘keyboard search,’ tried the contour thing and even knocked something out in the ‘rhythm search.’ Bupkis. More often, it emits an error during processing my pitiable attempts, so I don't even know if it can actually find anything with those offending inputs.

There's also Midomi, into which I similarly whistled, hummed and even made some endeavors at singing, and likewise got no luck.

I feel like there indeed should be a music search engine that works from whistling, but I haven't encountered one so far.

In a vaguely topical sentiment, I several times had success with Audiotag.info—but you need a piece of the actual music there. It worked better for me than Shazam, SoundCloud or Picard. Probably because I'm unlikely to be looking for a hit song—now, ‘William Tell’ on a xylophone is closer to my thing: https://www.youtube.com/watch?v=gXajSUb29ZY (also related: https://www.youtube.com/watch?v=mRXUzWNdLx8&t=9m40s).