Maxperson
Morkus from Orkus
I would actually lean towards coming out in some other plane. Probably the ethereal or astral. When you teleport you travel through some other dimension. Since the spell goes out without a hitch and you vanish, but are unable to reappear, I'd say you are stuck in that other dimension.Pointing out the DM can count due to peanuts being in his throat is not good.
....if you Thunder Step(or other teleport) into an anti-magic area? The reappearance is magical, so would be blocked. The disappearance wasn't in an anti-magic zone, so it goes off without a hitch.
If I was being nice, reappear just outside the zone.
If I was being nasty, spell fails since you can't reappear in the zone.