Adobe stock credits disappeared

Did you downgrade your plan? Did you acquire credit packs and didn't use them during the year?

As @Jill_C suggested, you should look into your licence history.

If you are still wondering, what happened, I recommend to contact Adobe customer service. Adobe customer care can be contacted by beginning a secure chat session at https://helpx.adobe.com/contact.html?rghtup=autoOpen. Pop-up blockers need to be disabled! If the chat window fails to open, or is non-responsive, use a different device to start the interaction.
Support phone numbers may be found here: https://helpx.adobe.com/contact/phone.html. Please note that phone charges may apply.

For support via Twitter:
https://twitter.com/AdobeCare

(see also here: https://community.adobe.com/t5/creative-cloud-services/how-to-contact-adobe-support/td-p/11875703 or here
https://community.adobe.com/t5/account-payment-plan/how-to-contact-adobe-support/td-p/11843852)

Look at your Licensing history for recent licenses. Is it possible that someone else has access to your account? If not, contact Adobe directly since we here in the Forum have no access to your account.