Sorry to hear about this, but don't let it dishearten you from making games and open sourcing them.

Someone stealing your code doesn't take away from the fact that you accomplished your goal of making a complete game. And from what you just wrote - that was your intention.

Regarding your blog title, I'd add 'timing' as well as 'marketing'. Titles of both submissions were remarkably similar ("Flappy Bird in HTML5" vs "Flappy Birdy html5 clone created using the Phaser framework"). Maybe the timing of your submission was off.

Also you can now state that you're the original creator of all the HTML5 Flappy Bird clones that have been popping up recently.