No access to confirmation number of purchase

Hello, team! Unfortunately, we can send our inquiry to the support because we can’t log in due to the missing confirmation (purchase) number. We are using your theme for the website stated below, which had been purchased from another agency (not us). However, we are not working with the third party that has purchased the theme anymore and therefore, we have no contact. We don’t have access to the account in themeforest, and we can’t update the theme to its newest version – we are still working with version 3.5. The Avia builder stopped working. Please, let us know how we can procede in this situation.