I lost all my LP from a bug or smth.

I casually started a ranked game this morning. I won the game and got a 19 lp reward. When i looked at my profile to check how much total lp i had it was only 19 which is weird considering i won 3 games before this one. I dont know if i will come back or not which is why im writing this. I would like to atleast know what the hell happened. Thanks