It could have been a mathematician , you never know with that Anon guy.
If it's not your field you might well not bother to write the paper. (After all, it's not your field, somebody might have solved it since it didn't seem that hard, and do you really want to do an exhaustive literature research for a fun puzzle you worked out?)
There's a lot of people like that in maths. Very talented but dropping in and out of it or doing it recreationally.