[f5fstop]

I would recommend you take the vehicle to the dealer and have them troubleshoot the problem.
The way the system works, the SDM should not have signaled the Onstar module to call unless there was an actually deployment of the air bags.
If there was a signal sent to the onstar module, there should be a code in the system that the dealer can read. Then again, your SIR light should have come on too. So, it sounds like something is wrong in the system somewhere.

As for the person who hit the deer, be glad your bags did not go off. Frontal bags are designed to be deployed based on deceleration not impact. That sensor(s) up front is used by the SDM to determine what stage of air bag deployement should be exercised; stage one or stage two. Stage one being less of a force than stage two.
Hitting a deer is not a sudden deceleration, as hitting another vehicle or a brick wall. After hitting a deer the vehicle moves forward and does not decelerate rapidly.