If I could locate the nest, I might have been able to put it back.

[xxwzs]

The following reading material comes from "Chinese College Entrance Examination (2017)":

I work with Volunteers for Wildlife, a rescue and education organization at Bailey Arboretum in Locust Valley. Trying to help injured, displaced or sick creatures can be heartbreaking; survival is never certain. However, when it works, it is simply beautiful.

I got a rescue call from a woman in Muttontown. She had found a young owl on the ground. When I arrived, I saw a 2- to 3-week-old owl. It had already been placed in a carrier for safety.

I examined the chick and it seemed fine. If I could locate the nest, I might have been able to put it back, but no luck. My next work was to construct a nest and anchor it in a tree.

My questions are:
1. Is the underlined part related to subjunctive mood? If so, why the author used 'could locate' instead of 'could have located' to talk about an unreal situation of the past?
2. If 'could locate' can be replaced with 'could have located', is there any difference between them?
3. I have referred to several textbooks on English grammar (Chinese version), all of which say 'could/might have done' can be used in a if-clause to talk an unreal situation of the past, but not 'could/might do'. Is it correct?

 

[SoothingDave]

No, it's wrong.

"If I could locate the nest, I might be able to put it back" (situation is still ongoing)

or

"If I could have located the nest, I might have been able to put it back." (situation is over, this is counter to what actually happened.)

 

[Tarheel]

Try:

My next task ....

Or:

My next job ....

But not:

My next work ....