I asked this question two weeks ago (Unable to recover Google API project and "This client ID is globally unique and is already in use.") and was immediately approached by a Google representative who promised to get back to me. Unfortunately this Google employee vanished in thin air or was sucked into a black hole or something. He hasn't been on SO since September 30th and all my efforts to get in touch have failed. I'm posting here again in then hope that some other Google employee might answer and follow through.
The question once again:
I've been working as a consultant on an Android project that uses Google oAuth2 to authenticate and identify it's users. The Android project is in production and available for download on Google Play. The oAuth client ids and the entire Google API project was setup by me using a Google Apps e-mail address setup in my name on the client's domain.
Since the project has been released and my work with the client is finished my e-mail address has been deactivated and subsequently deleted (or so it seems, the client claims to not being able to recreate it). Since my e-mail account was set as the owner of the API project the deletion of my e-mail address has resulted in the deactivation (or deletion) of the API project as well. This has of course seriously crippled the app in question.
To get things up and running again a new e-mail address was set up for me on the client's domain and I created a new API project. The problem is that I'm unable to create the oAuth client ids since the packagename and SHA1 key are the same as for the app already live. I get the "This client ID is globally unique and is already in use" message and I seem to be stuck in a very awkward situation. I see a couple of possible solutions but I'm not sure how to proceed:
Reactivate the original e-mail address in the hope that the API project is still linked to that account
Reactivate the Google API project with the help of a Google engineer and assign it to an e-mail account on the client's domain
Delete the client ids from some Google database with the help of a Google engineer and setup a new API project and release a new version of the app.
Worst case: accept the loss, change package name, release a new app and kindly ask users to migrate to the new app.
I've read that Google monitors the google-oauth tag here on SO and I hope to get some help either from the SO community or Google itself. Many thanks in advance!