The buds would have come apart before any substantial G forces were exerted.

If you have been exercising for some time, then it may have just been a random trigger of vestibular systems. Plenty of things can trigger vestibular issues besides a concussion.

Maybe the ear buds caused a brief negative pressure to your ears as they came out.

I experienced severe vertigo last night for absolutely no discernible reason. No changes to my routine. I have never experience that before.