Homework advice: if you've got a clever mind, help please?!?!?!?!?!?!?!?

I need to help! I ALWAYS do my homework! But, Monday I didn't do the warm-up, and my teacher is not that gullible; she excuse has to be convincing. Please help me with this! I need help basically to show that she forgot to stamp my warm-up for whatever reason. I just don't know what to do? She stamps our warm-ups (which are worth 5 points), and they are stamped on our agenda. So, it's not that hard to fake I think? PLEASE HELP! THANK YOU, APPRECIATE IT; AND DON'T SAY, THAT'S BAD OR SOMETHING! jUST HELP IF YOU'VE GOT HELP! thanks AGAIN