Don't worry, but look for signs of damage throughout the house. Look for paint missing from the walls or threads hanging off the sofa where they weren't before (lol). Also, set out delicious fruits and rat mix near her cage, and make sure it is clean. Set out a small dish of shallow water near her cage (so she doesn't dehydrate on her adventures around your home)and make sure all cats are out before you close the door.
Before you leave for the night make sure she has a way back in to her aquarium such as a book with a textured cover (propped against the side) or a pile of dirty clothes will work (set near the tank) since you're going to wash them anyway. Make sure the cage in on the floor since rats can jump down very easily but may not be as great at climbing back up unto a table or desk. Aquariums are not the best suited living environments for rats but if that is what you have then that is what we shall work with.
If you need more help just PM me, I'll be glad to try. I have two rats and three cats, so I understand how you feel about one escaping. Oh, and make sure that your other rat's cage is secure from the outside, since the escapee might try to sneak in.