If that final game was a loss, then it’s possible your final adjusted rank really is platinum 1 in which case this was likely due to the 7 win 20 loss system preventing you from seeing your true rank. However, if you believe this is a bug, I’m linking my post in case you would like to read more about this issue: Comprehensive Thread Of All Top 500/Competitive Bugs. I put your thread under: Incorrect/Missing Competitive Rewards For All Ranks (Seasons 1 & 2).