I’d start by calling EVA.

If you have the EVA PNR UA gave you, you can give them that. If they can’t find you, that’s going to be an issue. That way you know for sure, and can call UA so they can work with you to get your flight back, or give you an alternate.

Note that often on bookings that involve partners, the segments that are after the last UA operated flight don’t necessarily show, but that’s not typical if booked through UAs website.