2023 LEXUS RX Steering Problems

Hi. I noticed my vehicle was randomly making a clunking noise in the rear end. Also, on the highway, it would drift and was difficult to steer. I took it to dealership to be examined because it was still under warranty. They showed me that the driver's side rear trailing arm was disconnected. The bolt was not even there. They stated that it was caused by outside influence, possibly from hitting something. But I did not hit anything. The only sign of damage was where the loose trailing arm rubbed against the steering knuckle. They also told me it was too dangerous to drive off the lot. Because they claimed outside influence, they did not cover it under warranty. I took it to my mechanic. He believed the bolt had come loose on its own. He thought this because the trailing arm bolt on the passenger side was very loose...