Increasingly Worried

We went to bed last night with 2 cats and woke up this morning with 1. Sometime during the night, Roxy disappeared. Mind you, this isn't in the wilderness of the Adirondacks where the cats roamed free all summer. This is our 800 sq.ft Manhattan apartment (!). It was at first amusing and now we are freaking out. We've double-checked windows and all her nooks and crannies. I truly hope this has a funny and happy ending from our quirky Roxy.