After the first few weeks, he had lost track of time.

I lost track of how many times we made love.

Then he lost track of everything, and knew nothing more.

Thought he'd lost track of the girl, only she turned up the following week at another party.

I had just lost track of what was going on.

Or perhaps because he lost track of the results too quickly.

She'd probably lost track of what she wanted to hear.

Department officials said they had lost track of the money.

By then, he had lost track of his wife and baby.

And in the end, I lost track of the time.