Animal shelters and agencies in particular are always understaffed and overworked. Don't rely on them to remember your pet and call you back. That's not meant as a criticism, only a recognition of their heavy stress and workload. Be sure to ask if anyone has brought in any injured pets that aren't theirs. If they have, and it sounds even remotely like yours, be sure to visit and see the animal in person.
Descriptions are generally vague.
Ten people hearing the same description might picture 10 very different animals. Only the owner really knows what their pet looks like. Consider offering a reward for information or the return of your pet. Animals, particularly cats, can get into smaller areas than you might think. Stop often and listen carefully.