Scrape the clay off the couch using a dull butter knife or plastic knife. Do not use a sharp utensil on your couch as it may tear it.
Dab a cotton ball with an isopropyl alcohol. Rub the alcohol-soaked cotton ball over a small portion of the stained area. Do this test before soaking the entire area with the liquid. This will help you determine how your couch reacts to alcohol before complicating the stain.
Examine the area after one minute. If the couch did not discolor during your test swab, continue working on the area with alcohol and a clean cloth.
Scrape at the softened clay and remove it. Soak the area again until you have removed all the Silly Putty.
Spray a small area of the couch with a spray lubricant like WD-40. Allow the lubricant to soak in the fabric for about one minute.
Scrape at the clay with a butter knife or stiff rubber spatula. If the Silly Putty responds to the spray well, without staining the couch, continue to spray and scrape at the spot.
Rub the area with a soapy cloth after you have removed all the clay.