I forgot the Google account name that I used for buying apps on Google Play, can I recover it somehow? I am not sure if this fits here, but I saw a couple of other account related questions, so I'm giving it a shot.

I just resetted my phone and forgot to take note of one of the two Google accounts I had on it, which I was using to buy apps on Google Play and to save some contacts.

The account is not linked to a recovery email, nor is associated with a telephone number. I fully remember the password but only a good part of the username. I never used the account to email anyone at all, not even my other Google mail account.

Do I have any chances to recover the account username given that the account also has a Google Plus profile, and that nobody else except me could be able to tell exactly the Google Plus profile associated with that Google account name for which I remember a substantial part (the G+ account has been configured to not pubblicly show email) ?

I also thought I could contact a developer for an app I bought, and see if they have access to the emails from which they receive a purchase. But I have been told that as a developer you can search order details only starting from the email itself...

Any other ideas? What else could I do? If I don't fix this, I will loose all the apps which I've bought on Google Play and all the contacts saved on that account... :\

I hope there's a a way. Thanks!
In my opinion you should search for devices that you might had linked that account and check if someone has that email address. Think if you ever sent a email using that account to a close friend, family member or other internet service. 

You can also take a look at this forum answer: https://productforums.google.com/forum/#!msg/gmail/ydNElvUjJVU/hNjOMBN0dNYJ