Sutures and membrane fell out next day after bone graft, can the graft still be used?

You should check with your dentist as sometimes the bone graft does fail. Pain with an extraction can last for 10-14 days. This does not mean that your bone graft has failed. Sometimes a new bone graft will be needed if the first one does not succeed.  Usually, bone grafts will take within 3 months. Your dentist may want to do another bone graft within a few weeks to make sure you have bone for your implant. The best to you.

Hi:It's best for you to go back to your surgeon to inspect the area right away.  It is difficult to give you accurate advice without X-rays and clinical exam.Best,Dr. Maddahi

It is certainly possible that the bone graft has less chance for success based on what you're saying. You should definitely go back to the person who did the treatment for evaluation. 

it is difficult to say anything without seeing yr case. it is my request to upload yr intra oral graft site photos.