In the beginning of episode 1 of Digimon Tri, we see glimpses of the second generation Digi-destined (Davis, Yolei, Cody and Ken; sorry I only know their English dubbed names) being destroyed by what looks like Alphamon.
Hikari and Takeru are technically also 2nd generation Digi-destined, so why weren't they with Davis and the rest when they confronted Alphamon?
Now that the last movie has been released, we learn that
Daisuke and the second generation DigiDestined discovered Yggdrasil's plans quickly, and were quickly dispatched of at the orders of Himekawa. As it turns out, Mr. Nishijima placed them in the Digital World at Himekawa's orders.
During the events of the final move, we learn that
They are in the Digital World, in a life-support chamber room of sorts. It is not entirely clear if they were on the verge of death, or if they were deliberately hidden there, but it is implied that they did sustain some physical injuries. They are transmitted back to the real world as a dying act by Nishijima, since the room they were in blew up after they had been transmitted.
Unfortunately, they don't feature much at all during this movie series.
Hikari and Takeru are both 1st and 2nd generation Digi-destined, so they were probably with the former group while the latter group was destroyed by Alphamon. Otherwise, I'm not very sure, and it's a question that will be answered in the next few movies.
