There are some particles that don’t interact via the electromagnetic force. There are some particles that don’t interact via the strong force. And there are some particles that don’t interact via the weak force. All the particles we know, we’ve detected because they interact via at least one of those forces—but there’s no rule that says a particle must interact with any of them.
Why should we assume that every particle in existence must be conveniently detectable? It’s like a blind person assuming nothing can exist unless it makes a noise.