Consider setting a humane trap
Inside cats that “escape” to the outdoors are very likely to be hiding close by. Their instinct when frightened is not to reveal themselves, so they will not meow or come to you. The only way to get them back may be to trap them. Some local humane societies and rescues on my links page will lend or rent humane traps. Bait with some strong-smelling food. Monitor trap often. If left overnight, do not be surprised if you catch a raccoon or someone else’s cat!