So I lost my promo although there was a loss prevented involved.

I cannot quite understand how loss prevented works. I was on my promo to silver II and I lost it but my 1st game was a loss prevented and even after the game I checked the "Leagues" in my profile which didn't show an "X" making me feel comfortable that the defeat didn't count. My last 2 rankeds were a victory followed by a defeat but after the defeat, I was surprised to see that I'm no longer in promotion series. To conclude I lost my promotion series without actually losing a second game. I'm asking if that is a bug or loss prevented games actually count against you. Proof: http://prntscr.com/9xr4cn (ignore the Illaoi game)