More seriously, in 10K years we may be the first to even care about running simulations that detailed. There must be a first for anyone.
If there are glitches in reality or a wall that we hit and somehow fall of the edge of the universe, then OK - it may be a sim. But until then, assume everything's real and that belief that we're in a sim is no different than the superstitions of sky gods that watch your every move and will smite you if you don't follow their extremely vague and conflicting instructions or the superstition that the earth was flat and you may fall of the edge if you cross the Atlantic or that the universe is balanced on the back of four elephants themselves standing atop a giant-ass turtle.