I don't really understand how dev options would be relevant: if FRP has been triggered then the phone has been reset, and hence by definition dev options have been turned off (because that's the default state, and hence the state that a reset will return it to).
And I'm afraid that the reason nobody would post a solution here if they had one in the first place (and to be clear, I don't) is that it would tell any phone thief who could use a search engine how to do it, which would be highly irresponsible.
Your best bet is to contact an official service centre, with proof of purchase, and see whether they can do anything. It won't be free, but you may have to view it as a learning experience (the lesson being "make sure I know my account passwords before doing a reset"). Sorry, but that's all I can suggest.