There are several possibilities when you received a notice saying the package is delivered but you did not see it:
1) It is deep inside in your mailbox. Please check it again.
2) It is placed at your doorway, front porch, or at your front door. Some customers use their garage to enter the house, please check the front door.
3) You family member might have received it on your behalf but forgot to tell you.
4) The package was mistakenly placed in your neighbor's mailbox. You may ask around your neighbors to see if anyone has received a package.
5) The postman took the package back to the local post office after scanning by mistake.
If you have checked your house and neighbors but cannot find it, you may visit your local post office to ask the postman if the package was taken back.
Please keep us posted about the fate of the package. In most cases, the package can be recovered.