Hyaenodon was so named because of an imagined similarity between a fossil tooth and those of modern hyaenas.
but the creature has proven to be far from any sort of a hyaena in form or function. in fact, as a creodont, it did not even belong to the order Carnivora.
could a creodont survive since the Miocene? anything is possible, but Pleistocene survivors would seem far more plausible than Miocene.

that small illustration in the above article of a Dire Wolf confronting a smaller carnivore (“NOVA image”) is interesting in that the smaller creature resembles the Shunka mounting. it would be interesting to know what the artist was rendering there.

as for Dire Wolves, it seems from most literature that they are not so dissimilar from modern wolves, merely having minor morphological differences that require examination by a trained eye, such as skull shape and shorter legs.
if Dire Wolves still live, most observers would consider that they had seen a known wolf breed and think nothing more of it.
tales of monstrous sized wolves possibly indicate something else like the involvement of imagination and myth-legend cycles, perhaps.
or perhaps individuals of known species afflicted with gigantism leading observers to assume that they represent unknown populations of giants.