Well even though you have been a jerk to me I will be happy to tell you how to fix it. Of course there are plenty of aftermarket shoulder pads you can buy but if you want to preserve the one you have you can do the following things.
1. you can sand the pad to be more grippy. Stay away from the thread.
2. you can find some suede and glue it to the pad. I like this better because then you don't have to take a chance on doing the sanding wrong and with a full piece of suede you can always rough it up again easily with a suede brush. You local leather shop will have scraps and if you go visit them then it's likely they will find a suitable piece and cut it and glue it for you. Use a good contact cement and follow the directions exactly. You can also have it sewn on by a luggage repair shop. But if you use contact cement and do it right then it will never come loose. You WILL need to lightly sand the shoulder pad though if you do the suede.
3. There is a product called bag stop or something like that which glues on to existing shoulder pads with self adhesive tape. Never used it but you can probably find at the luggage repair shop. Google around and you will probably find it or similar products.