Spokes for Shimano Ultegra Wheelset
I recently went through a similar process with my Easton EA90 SLX wheel.

In my case, 2 spokes broke at the same time (or one immediately after the other).  After special ordering the spokes from Easton and lacing them up, I quickly realized that the rim was bent beyond the point of repair.

The fewer spokes your wheel has, the higher the spoke tension needs to be.  With such a high spoke tension a broken spoke can not only cause the wheel to become un-true, but also cause the rim to bend (which permanently weakens the integrity of the rim).

I would recommend taking it into your LBS, and maybe even sending back to Shimano for inspection.