What have you done to promote germination? For almost all iris including siberica, I like to give them a warm moist period of 2-4 weeks, then a moist chill of 40F for a month or more before bringing back to warm. Fall sowing outside works great in my Z8b. Not all seeds will germinate at the same time, they could be scattered over many days or even weeks.

No matter which iris, the seedling makes it's appearance like the tip of a pointy sharp blade of grass. Pics of iris seedlings here although not siberica but which will look same:

Here is a link that might be useful: Seed Site