1.   After the war they lost track of each other.

2.   Billy had lost track momentarily of where he was or how he had gotten there.

3.   But he was starting to lose track of the things that had made him what he was as well.

4.   Despite his precautions, he sometimes loses track of her and she is left unattended.

5.   He lost track of her after her family moved away.

6.   He used to wander over the moors, losing all track of time.

7.   I had the file on my desk a minute ago, but I seem to have lost track of it.

8.   I just lost all track of time.

9.   I lost track of the rest.

10.   I must have lost track of time and my destination, because when I got to the house, it was seven-thirty.