A link to the inaturalist observation and commentary from working mycologists:
https://www.inaturalist.org/observations/168461910?fbclid=Iw...
(tl;dr image analysis seems to suggest the images haven't been doctored, mycologists like Alan Rockefeller believe it's most likely been dislodged and stuck to the frog's skin somehow, mycena mycelium would not colonise a frog flesh substrate)