If you cannot find your event on the Eventportal, please check the event's public channels. These will initially be the official website of the event you attended, the official app, or a social media channel.
If the event used Eventportal for topups, they will usually announce how to get a refund of your remaining balance after the end date of the event.
If you still cannot find your event, please contact the promoter over their official channel and ask for a payout there.