Another counter to this is to remember that the other players can't see the character. Have the invisible player pull his mini off the table, sit next to you, and tell you where he is moving.
It will make getting him healed, buffed, or excluded from AoE spells a nightmare.
That said, I would expect a straight up perception check to work. I think "because mythic" isn't a very strong logical argument.
It would imply any ability that could normally detect the invisible can get a "mythic" association and then see this.
Mythic See Invisible as one example.
