Is there a way to know if a resource was just created rather than just giving you the output of an already existing resource?

Not from pure Pulumi code. That's a side effect of the desired-state / declarative model. In many clouds and for many resource types, you could register a listener for the resource's creation in a project that you deploy before the project in question. Remember, all of your Pulumi code is run before any of it is deployed. You cannot ask "has a resource been just created?" because, at least in theory, no resources have ever been just created at that time. If they're to be created, it'll happen in a few seconds, once the Pulumi engine gets going.