I won't say that it was "entirely his fault for having such a non-standard workflow". It was just as much your own fault, for not having the wisdom, the intelligence or the experience to realize that users will do all kinds of stuff...
It's a 50/50 case. You were at fault, he was at fault.
It's important to remember that users are never at fault for not having the same amount of IT-knowledge as you do yourself. If they did have the same amount, they'd be doing your job, and they'd be your colleagues.
Biting the hand that feeds IT
