A growth spurt timed challenge was to finish today (03/08/2018) but it disappeared from my app before the timer ran out, and a new event has taken it's place. Either a new event happened and the timer was incorrect for growth spurt, or a whole new timed challenge has taken place and I have not gotten my rewards.

Is this a normal bug for events to disappear and your rewards with them, or is this just a bug on my end where I will still receive the reward for the place I took?

this is because you have leveled and you got rune lords now instead. Last week someone had the same issue https://forums.socialpointgames.com/topic/5817/challenge-dissapeared