I believe the word that best fits your description is simply "lose":

11-a. To elude or outdistance: lost their pursuers.

 

11-b. To be outdistanced by: chased the thieves but lost them.

"We lost the signal.", "I don't want to lose sight of the captain.", "He lost the animal's silhouette on the horizon." are all clear and unambiguous.

I believe the word that best fits your description is simply "lose":

11-a. To elude or outdistance: lost their pursuers.

11-b. To be outdistanced by: chased the thieves but lost them.

"We lost the signal.", "I don't want to lose sight of the captain.", "He lost the animal's silhouette on the horizon." are all clear and unambiguous.