>>58198590
After some digging, I can answer the question myself now. The artist had multiple accounts, being Mermeirin, Putridpastries (both deleted) and Pichupurin (still active).
>>58198732
Fortunately, Tumblr's sharing system is so broken that each reblog creates an independent copy of the post; meaning even after an accounts deletion, the associated files still exist in the reblogs. Though finding out who (and if someone) did that is a pain in the ass, as there is no option to search by reblogs: not to mention search engines don't give you many results, for some reason.
