Accidentally licensed several Adobe Stock images

There is no possibility to "return" licences. You could, however, contact adobe customer care to ask them to assign you back the lost credits. 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.

(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)

It's possible to inadvertently licence assets, if you push the "Licence" button, but it never happened to me, and I'm surfing stock a lot.