Energy is not lost, but it is expended in different ways when different objects collide.
A more visceral statement of these principles:
Drop a rubber ball on the floor. As it hits the floor it stores up spring energy inside itself, and then bounces back almost as high as the start point, losing only a little energy to friction.
Drop a hard billiard ball on the floor. It bounces a bit, but much of the energy gets spent making a dent in the floor.
Drop a sphere of soft clay on the floor. It goes "splat" - most of the energy is spent pushing the clay out sideways. (There may be a small crown on the blob of clay on the floor where some of it did bounce back a bit.)
Drop a human being on the floor. Where does the energy go? It goes into bruising skin and muscles, bouncing internal organs back and forth, forcing air out of the person's lungs, swear words, etc. It takes quite a forceful impact to have enough leftover energy yo make a human being bounce enough to see.
The concept of a spherical cow is often used to describe the way real-world objects are simplified to make the underlying physics easier to describe; in this case you seem to be thinking of a spherical person.