Uncover: Quickly Discover Exposed Hosts on the Internet from Linux
No doubt, Shodan is an amazing way to find devices connected to the internet. However, it is not the only search engine. There are several platforms like Censys and Fofa that offer you the chance to check if the device is connected to the internet.
If you have a list of IP addresses and check it on Shodan (to know whether they are exposed to the internet), in a very rare situation, you might not see any result declaring that they are not exposed.