From their FAQ [mccormickandschmicks.com]:

Question 3: I forgot to use my Preferred Guest Membership Card on my last visit—how do I still receive points?
Answer: As long as the date of your visit was within the last 3 months, you can receive points for your dining experience. There are 3 ways you can submit your request:
• Click here [mccormickandschmicks.com] to access the online Points Request Form

Question 6: How do I redeem points for rewards...