Ideas
Keep on trying to catch an angel fish even if it doesn't show up for the quest any longer. It's one of the ingredients for ambrosia, so I'm sure we'll need it in the future.
You haven't lost the challenge. It doesn't really matter if you missed a step, as long as you got enough points to collect the rewards for this week. Even if you didn't get all the rewards, there are probably extra points built in. There's still 3 weeks to go, with 2 extra weeks after that, so there's still plenty of time.
Wait... does this mean we can still get all rewards even if we cannot complete all tasks for one week? Because I'm unable to complete week 3 as well - I went into CaS because one of my Sims needed new clothes, and when I went back into live mode, the remaining quests (go fishing with bait, travel to the Magic Realm) were gone. Fun fact: I still got all the rewards except the batfish which really doesn't make any sense because, like I said, I didn't complete all tasks.
When I go to the event page, it shows that I haven't completed all the quests - the one with "fish for the first ingredient" is still shown as active. In live mode, it's not there, though, plumbob is gone, too.
If I'm able to continue with next week's tasks, I'm fine with this, I guess, but if it broke the whole event, it'd be real bummer.