@lonestudent @XanderHenderson The answer was posted about 1 1/2 hours after the question was closed. As to how this can happen, please see
Submitting an answer to a closed question (and there are other related questions on the Meta site). Its accepted answer states it's a server side check, with a grace period of up to 4 hours allowed. I also saw a Meta answer once stating an answer was submitted just a few minutes shy of that 4 hour limit.