"return shall you return them": If he returned it (the animal), and it ran away; returned it and it ran away — even four or five times — he must continue returning it, it being written "Return shall you return them." If he returned it to a place where it could be seen (by the owner), he need not deal with it. If it were stolen or lost, he is responsible for it — until he returns it to his (the owner's) domain, it being written "to your brother."
(Devarim 22:2) "And if your brother is not near to you, and you do not know him, etc." "And if your brother is not near": I might think (that the halachah obtains) only if he is not near. Whence do I derive (that it obtains even) if he is far? From "And if your brother is not near to you." This tells me only of one who is far or near, when he knows. Whence do we derive (that the same obtains with) one whom he does not know? From "and you do not know him."