What came in my mind is - can be dark matter just bended spacetime?

It does bend space time since it interacts gravitationally.

But what if is this 'fabric' kind of plastic, and stay wrapped also when mass objects are gone in some special occasions? This would explain the gravity of dark matter, or why it does not interact with anything - cause there are no particles attached, just curved spacetime.

Would it explain dark matter? Have you checked that your idea actually corresponds to the observations? What you're proposing is effectively a modified gravitation theory, so you better be sure it fits observations even better than Einstein's theory, or else it's a non-starter.