I stopped by EC2 instance to do some maintenance and after I started I got a new IP. bummer. I made an elastic IP to make sure it does not change again, but i still have people calling the old IP, is there any way to claim that recently lost IP associated to my Ec2.
No, you can't get that old public IP back. Try to always use DNS names to avoid this kind of issues in the future.
Look at this official answer to a similar question.