Tamara...
From my experienced... the average of found for cats.. 4-48 days..
why it takes so long.. for example if its you.. found cat outside.. took in and take care for while and look for ownership or.. decided its yours because the cat is so beauitful and friendly.. in around 30 days later, you feel that cat needs to be checked with vet to have vaccianted... By the time, the vet will scan the cat.. to check.. "beep beep" ahh..
so by the time you will get the call in around 4days to 3 months....Or.. its been while for you like more than 2 days, I would start looking on ditches or side of roads.. just in case.. if the cat have been hit by car.. so you know either missing or killed..
Good Luck and wish you the best.. I know its hard.. to losing the pet..