That's a MAJOR fail on the part of the airbag, unless there were multiple impacts and it deployed on the first impact, not able to help in further impacts. But that's not what you describe. A couple seconds late, big fail. Some GM cars had zero deployment because the detent was too soft and with many keys hanging low in the ignition key slot, the impact force turned off the ignition, disabling the airbag, before it could deploy. And after it happened a couple times, the engineer involved implemented a running change on the design without filing a formal revision or notifying anyone, when people could have been saved. That was discovered at the beginning of Mary Barra's tenure. She didn't do the normal thing and deny and fight/delay in court, GM ponied up and paid damages to all, settlements administered I think by the same attorney that handled 9/11 settlements. And the engineer was terminated, not scapegoated, they violated a major procedure for safety reporting and engineering changes, they deserved to be fired.

Getting back to you, I suppose if the truck hit your windshield before your bumper contacted the truck and triggered the airbag, maybe that's a viable explanation. But with normal contact of a vehicle or fixed obstacle, that airbag is supposed to be triggered *fast*, and inflates fast. Milliseconds. So fast that first generation airbags were a bit too fast/severe for lesser collisions, so they implemented a design that could deploy at one of two different settings based on collision severity based on g-force.