Question on the Event

If I were to start a new character and finish the event this week but not claim the rewards, would I be able to still retrieve the rewards after the event is over (notably after unlocking Mayhem so I could farm for a good anoint)?
I’m asking because the Bloody harvest event tab stayed after bloody harvest is over but I’ve heard someone say that if you play offline, the event isn’t there and that I might lose any unclaimed rewards once the event has ended.

Why wouldn’t you claim the rewards? They’re max level regardless.

Because, it’s gonna be a new character, as thus, can’t do Mayhem Mode yet. And if I want a good anointment on it, my chances will be best on Mayhem 3 or 4.