Were ever found Dinosaurs fossils from people in ancient times? What did they think of them?

As far as I know, there is little conclusive evidence that ancient peoples found dinosaur fossils and then directly incorporated them into their cultures (which would in turn serve as our evidence that they found them). To quote one paleontologist, "We cannot rule out the possibility that ancient peoples attempted to reconstruct fossil animals, but any suggestion that they did is currently largely speculative," (Witton p. 18).

Issues with Dinosaur Body Fossils

Most dinosaur fossils are not beautiful finds like the T-Rex Sue or the famous Archaeopteryx everyone knows about. As an example, I created a table with every fossil found from clade Carnosauria in both Alta and Baja California as of the early 2000s (Hilton 2003).

Type	Element	Age
Carnosauria	Phalanx	Late Cret
Carnosauria	Teeth	Late Cret
Carnosauria	Phalanx	Late Cret
Carnosauria	Teeth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Manus Phalanx	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret
Carnosauria	Tooth	Late Cret

Things to notice:

These are from the most recent epoch of the Mesozoic.
Most of these are miniscule fragments (a single tooth here, a phalanx there).

We can talk about issues affecting preservation, paleoecology and distribution, etc., but the point is that most dinosaur body fossils difficult to identify as such.

Adrienne Mayor

Adrienne Mayor is a classicist at Stanford University who focuses on the relationship between fossils and myth and culture. She has argued that various cultures have found fossils and incorporated them into their artistic traditions and cultures.

Here are two examples. Both of the above are trace fossils formed by the behavior of dinosaurs, rather than body fossils of the dinosaurs themselves.

Lesotho: Lesotho has a decent collection of dinosaur trackways, which some researchers suspect might have inspired these cave paintings..

American Southwest: Adrienne Mayor has also argued that certain Southwest peoples such as the Pueblo and the Hopi use gastroliths in their pottery-making.

Note - in her book The First Fossil Hunters, she also presents the argument that ceratopsians from the Gobi Desert region inspired legends of griffins (Mayor 2011). I was not convinced that the ceratopsian finds really did inspire the griffin legends and artistic motifs and thought much of the evidence was circumstantial.

EDIT: To clarify, I am not sold on any of the proposed dinosaur explanations, but I think that the griffin one is the most doubtful.

References

“Footprints of Megatheropod Dinosaur Found in Lesotho.” Sci News, 26 Oct. 2017, www.sci-news.com/paleontology/megatheropod-dinosaur-footprints-lesotho-05363.html.

Helm, Charles W., et al. “Interest in Geological and Palaeontological Curiosities by Southern African Non-Western Societies: A Review and Perspectives for Future Study.” Proceedings of the Geologists' Association, vol. 130, no. 5, 2019, pp. 541–558., doi:10.1016/j.pgeola.2019.01.001.

Hilton, Richard P., and Ken Kirkland. Dinosaurs and Other Mesozoic Reptiles of California. University of California Press, 2003.

Martin, T. Introduction to the Study of Dinosaurs. Blackwell Science, 2001.

Mayor, Adrienne. The First Fossil Hunters. Princeton University Press, 2011.

Mayor, Adrienne. Fossil Legends of the First Americans. Princeton University Press, 2013.

Witton, Mark. The Paleoartist's Handbook. Cronwood Press, 2018.