To keep the contest discussions and the map submissions separate.
I recommend you talk to Idolon about submitting your map after the deadline.
Also: the main discussion thread had a link to the upload thread (and the upload thread was constantly being updated with new entries), since you're wondering how you were supposed to know about it.
It says so right under the header:
In hindsight though, on such a large thread it is kinda easy to miss...
This is why it's important to read the rules carefully. 65 other people (many of whom are very new) didn't have a problem. I hope you thank ido profusely for making the exception.
Yeah, the only reason we made the exception was due to it not specifically being mentioned in the OP of the contest thread. It was referenced, but never overtly explained.