Corner weight and try start/stop again? Do a huge burnout, check tread depth before and after.

I had the same problem when one of the axle hub nuts backed out after a rear wheel bearing change, the hub started to back out of the upright and the bearings where sloppy without the pre-load and it would allow toe in on acceleration and toe out on braking or lift.
I was easy to tell by lifting the car and wigeling the tire.
I supose that a broken a frame bushing or loose aligment bolt would do the same but you would likley hear a clunk every time it hapened and need a large toe change to get a noticable pull like that.