On one of the videos it seems that there is still a rather large object on the gravel path, after the cop drops the smaller object by the body. The object the cop drops seems too small to be the entire taser.
During the two-handed execution, there is an object visible on the walkway a couple of feet in front of Slager's left foot. However, after the shooting, it is still in the same place, and Slager ignores it when he returns to the vicinity to fetch whatever he was after. Whatever he picks up appears to have been lying in the grass.
The object the cop drops seems too small to be the entire taser.
It's really hard to make out what he dropped. That's why it's so annoying that the NBC drive-by moron (Lester Holt) who interviewed Santana failed to pursue the issue.