I agree. Mass cannot ‘time travel’. By going back or forward in time, you would be increasing the total mass in the universe, and that’s a no-no............
There was already a thread today that proved time travel.
Some ancient civilization had a stegosaur carved in a relief right next to all the other animals of their time and location.
Obviously, someone from the post-fossil-discovery future time traveled back and drew one for them. Because the explanation that the steg was alive at the same time as humans is more far fetched.
No, you would only be changing the location of the mass with respect to it’s location in 4 dimensions.