A Google search for “remove silly putty from clothes” returns the following info on the top of the page:
Results 1 – 10 of about 20,200 for remove silly putty from clothes.
I suggest you try the search.
The first result:
Step 1
Lay the piece of clothing with the Silly Putty on it onto a flat surface and stretch the material until it is taut. It is important to have the material taut as it makes the process of removing the Silly Putty much easier.
Step 2
Depending on the size of the Silly Putty that is adhered to the clothing, you will need to soak a cotton ball or the tip of a cotton swab in rubbing alcohol. Once you have the cotton soaked with the alcohol, press it into the Silly Putty to transfer as much of the alcohol into the putty as possible. If necessary, repeat this step several times until the Silly Putty is thoroughly covered with rubbing alcohol.
Step 3
While ensuring that the material is still taut, gently scrape at the Silly Putty with a butter knife. The majority of the Silly Putty should come off the first time. You may need to reapply more rubbing alcohol and then repeat this step.
Step 4
Once the Silly Putty has been removed completely from the clothing, launder the clothing item as usual.
Years ago I froze the clothing, cracked off some of the putty, and repeated. This was pre-internet.