I began hiking the Verdugos in the early 1950s. I have never seen a mountain lion. Other areas yes, but not the Verdugos. I have, though, seen many bobcats, some that I took a second look at as they were quite large and had a longer tail then just a bobcat. I have never seen mountain lion tracks either, and one must remember that lions do not show claw marks like big dogs do.
The deer population is alive and well (they are eating my roses, ivy and tomato plants, regularly), as lions do love to eat them. They eat about a deer a week. That adds up to a lot of deer.
Never seeing lions in the early years when they had much easier access to the Verdugos due to lots of open space in La Crescenta, Foothill Boulevard was not that busy, and there was no 210 Freeway. This makes me wonder why there would be lions today with much harder access.