magic regeneration shield after being bounced regenerate rules faq

[Nidorino]

If I regenerate a creature then it is bounced back to my hand and immediately I cast the same creature again does it remember it had the regeneration shield

[Arix]

No. Once a creature leaves play, for any reason, it loses all memory of its previous existence. When it comes back into play, it's considered a brand new creature, untied to its previous form.