In my last match, quinn had used her ult and as she was using the sky strike ult move to go back to quinn I ate her as tahm kench, and after she came out she was stuck as valor for the rest of the game. She had none of the bonuses of the ult, basically a melee bird.
Yeah I've seen this bug, it can also happen with a Yorick ulting you, stays that way for the rest of the game. Pretty much just build as normal but maybe add a Hydra in place of blood thirster and look for assassination opportunities, usually you tend to keep the move speed bonus and attack speed from W, other times you get the passive procs applying and making some of your attacks ranged again. Frozen mallet is also good if this happens.
Also did you try exiting the game and reloading? not sure if this helps.
