He is not rob of his priest title. He is still a priest.
It just that nobody calls him out of his mistake. Think there is a mandatory training session for all priest from time to time, they calling it a retreat.
Here goes another story that my corrupted dad told me. Now with the rites of confirmation, usually for kids whom have gone through church schooling and given the rite at the 10th grade level. Now during the ceremony and when them kids were lining up to receive the blessing, my dad be like, go up there too son and get it over with. So if I have gone up there and the "magic" was put upon me, does it invalid it since I'm not on their roster?
once a person is baptize, they can not be unbaptized. In other words, can I say I want out from the church and so can they unbaptized me? The answer is no.
In this case here, the person was not baptize since it was done wrongly so they need to be baptize again. Catholics are too soft, they tends not to sue the church. Most likely, they go down with the ship. For those that do, they want money and they want out from the church. Sorry, we can't unbaptized you and you are still registered as a member of the church.