Most Helpful Girl
Perhaps with the simple "Hi" a year later from the split, he came around in memory of the time that year before when you both had called it quits, to remind You... He was still around and that he may just want to be friends.
If you Accidentally Missed his message, he may of thought you didn't want to respond. However, with This being your call, your choice, you have Two choices in which Now... You can either acknowledge it or Just... Forget it.
Good luck. xx0