No. Double strike is not the same as trample.
As long as the creature with double strike is blocked, and does not have trample, any excess damage will not happen, nor go to the defending player at all.
It's just the same as a normal attacking creature, being blocked by a normal creature in the declare blockers step. After declaring blockers, the blocker was Unsummon ed. In this case, just like your question, the blocker is not around to receive normal combat damage, would it then go to the defending player? It does not.
Thank you. Kinda strange though. Its like having 2 swords, you stab ur enemie with 1, and u just leave the other one hanging while u could use it to kill the next target.