I have also lost my credits but I didn't receive any emails about credits expiring so wasn't forewarned!!! Not happy at all!!!
Branching to a new discussion,
I understand your concern, but these credits were only valid for a year as per the migration terms. In order to get the expired credits back, you may subscribe to one of our Adobe Stock plans: Adobe Stock pricing and membership plan | Adobe Stock
Also, you may Contact Customer Care so that they can verify your account details and can further assist to get the issue resolved.
Please refer Contact Support FAQ: Unable to reach support through the "Contact US" link in case you are unable to reach support through the above-mentioned link.
Feel free to update this thread in case of any additional query.