What an appropriate way message a guy after he ghosted you for 3 days?

Im currently online dating and im getting a lot of ghosting which i consider no messaging after 24 hours. One guy continued the conversation after 3 days and I dont know how to respond because I personally find 3 days as excessive to not message someone and expect them to be okay with it
What an appropriate way message a guy after he ghosted you for 3 days?
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