Throwing the fish blanket you got on that great trip to Cancun with Harpo where you had so much fun going to the Cancun Walmart (really!) into the dryer with a dry cleaning sheet does not remove the cat urine smell from the blanket. It merely adds the fragrance of dry cleaner sheet to the cat urine smell, which is not a combination the big perfume houses will be rushing to market next season.
The cat urine smell is on the blanket because you did not chase Shirley around the bedroom to kick her out because you did not want to wake SH up after his third night of working until 4 a.m. so you thought, Well, I'll just leave the door cracked and she'll go out when she's good and ready, which she did, but then you forgot about the part where you closed the basement door so Laverne, who is much slower and not as sneaky as Shirley and you did catch her at 6:32 a.m. and throw her into Siberia, would not get back into the kitchen and bedroom and start whining and wake SH up, and blocked Shirley from getting to the litter box.
You see the problem here.
Even if I didn't.
So at 9:04 a.m., Shirley needed to pee, as cats often do after 12 hours of being denied access to the box, so she looked for the softest, most absorbent place she could find, which of course was the fluffy quilt on top of the fish blanket on top of the rug we got in Morocco, not the easy-to-clean tile bathroom floor or easy-to-clean wood kitchen floor, and let go.
Moral of the story: Chase your cat, no matter what. Or get an upstairs litter box.