i went from B4 to B1 with 1 Game, No Promos Think its Bug HALP!

Befor i started i was B4 57 LP I started to play a Casual Cancerous Round of Ranked Solo and in the Lobby screen my Teammates where G4 top Illaoi G4 jungle Wukong S3 mid Ahri (went 2/7 after 20 min against fizz was 13/2 a. 20 min) B4 me adc Jhin S4 Support Morgana https://matchhistory.euw.leagueoflegends.com/en/#match-details/EUW1/3979972135/2065028020859264?tab=overview ^^^^^^^ the game link After we somehow won that match i pressed on the winning screen button and went to the launcher greeted by a screen saying "Promoted to Bronze 1" Is this a Bug?
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