Sounds like 'The night of the storm' - short story by Dean Koontz.
Quoting description from Wikipedia:
"The Night of the Storm": a group of intelligent robots go on a hunting trip in the woods, where they learn that the myth of "human beings" may not be a myth after all.
I've got a copy in the 'Strange Highways' collection.
The protagonist is 'Curanov', a robot built in an automated factory more than 100 years ago. Like all the others, the purpose of his existence is to gain more 'experiences', and he is bored of climbing mountains, exploring the arctic, etc because he's always adapted to the environment. In response, he visits a nature reserve to go hunting, while modifying himself to have less extraordinary senses and strength.
As Curanov and his companions set off, they are warned that
"we get a dozen reports each month about `human beings' sighted in wilder regions northwest of here."
After hunting a buck, they find hints that something not a robot is in the area:
"There," Tuttle said, pointing at the ground before them. "Footprints," Curanov said. Leeke said, "They don't belong to any of us." "So?" Curanov asked. "And they're not robot prints," Tuttle said. "Of course they are." Tuttle said, "Look closer."
The consider following the tracks, but end up getting nervous in the forest and go back to their lodge. The discuss whether sentient organic beings are possible, but dismiss the idea.
One of the robots disappears with their rifles overnight. The find him 'terminated' nearby, and decide to leave. They are followed and attacked by men:
Tuttle had fallen back under the relentless attack of a two-legged creature that moved almost as a robot might move, though it was clearly an animal. [...] A fleshy face stared back at him from a dozen feet away, blowing
steam in the cold air. It was framed in a fur-lined hood: a grotesque parody
of a robot face. Its eyes were too small for visual receptors, and they did
not glow. Its face was not perfectly symmetrical as it should have been; it
was out of proportion, also puffed and mottled from the cold. It did not even
shine in the torchlight, and yet ... ... yet ... obvious intelligence