I've checked it, and you can also check in
modlog:
Autoban user: N/A in topic #0 by member #555506
You should also have received a mail into your mailbox, which would contain the approximate reason for your ban, like copypaste (plagiarism) or something similar...
So you should do some research and I'll also have a look in reporting threads, but if someone only used the report to moderator button then only a mod can give you proper answer about the reason.