A/Mo able to block all Hex, no error

I came upon an A/Mo today that was able to not be effected by any of my hexes (no color change in Healthbar). He was not using anything to remove the hexes. I got no error message, indicating that the spell hex cast successfully.

Someone in chat said Shroud of Silence or Shadow Form. In each case I would have seen an error message, so I think that rules those out.

Ideas?

Im not in game right now and i dotn feel like testing this but im pretty sure that with shadow form you dont get a error, it just makes the spell fail.

Spell Breaker also. - It just instantly fails, also obsidian flesh.

Spellbreaker gives you a warning after you try casting on them, though (if I recall). He could have been using Holy Veil to drop your hexes as soon as you cast them? But you'd have theoretically seen a change in his health bar in the time it took for him to drop HV...

It always mentions why it fails in these cases. it must be a monk dehex, or u cast the spell by accident on someone else, switching after. There is no spell that prevents hexes to land without a message being posted. (unless you can disable that via options?)