Couldn't have been izanagi even after ive explained it. Ill instead just upload a DB entry which hints towards kamui as the possible answer
You must be registered for see images
DB hints towards kamui. Secondly after izanagi works, he wouldve had to have used it before amaterasu therefore when he himself is an illusion he trolls amaterasu.
Apart from the fact that its hinted that its kamui, it further states that tobi doesnt use the ms in the presence of other akatsuki members. We do know that he used in the midst of konan/deva path though even then he was a few metres away he used it.
So basically, the DB has revealed that he is careful around akatsuki members when he uses the ms which we can translate as kamui. Db secondly hints that its kamui that he used to evade amaterasu. So what tobi said when he talked about hiding secrets from itachi otherwise he would be dead right now, links with the 2 evidence in the DB.
The secrets is the ms that he doesnt use in the presence of akatsuki members. Its this secret (ms that we can translate as kamui) is what allowed him to evade amaterasu. Which brings me to the fact that the DB supports not many people even knowing about kamui. Kamui far outweighs izanagi if we were to speculate
And Khaydz5 you need to calm down
