It'd be a clever tell if Eliezer wanted us to conclude they're still in the Mirror, but I don't think its absence is strong evidence of the opposite. The Mirror might not work that way, and Eliezer might simply have forgotten if it did.

(I would say it'd be clever if anyone walking into their dream-world died soon after of amino-acid chirality issues, but similar things have been done so many times that it's not very creative. Plus it clashes with the theme.)