Disturbing Steering Rack Situation

I took my 2007 Prius into the Toyota garage last week to get new brake pads and discs (highlighted at the last service as needing replacement after a further 5k miles) and to correct a 'drift' to the steering, where a centralised steering wheel would cause the car to move to the left.

After around 3.5 hours, the service assistant popped out to say that re-adjusting the steering had caused the entire system to seize and that the car was undriveable. It would take £1000 in parts and labour to replace the steering rack. As the car is only worth around £4,000, I informed the assistant basically, they have written off my car. I was offered a potential scrappage deal against a new vehicle (!!!), or that more hours could be sunk in to put the steering back to where it was originally - ie still drifting to the left.

Obviously I wasn't happy and escalated a complaint to management. Within five minutes, the manager came out and said that the issue had been fixed, the car wasn't dangerous to drive and would pass an MOT. I was told that the thread had corroded but luckily where it was fixed now had corrected the initial fault and the steering wasn't seized any more - BUT - the steering would never be able to be adjusted again without a replacement. Having been initially shocked, I was just happy to get a working vehicle to take home.

However, the more I think about it, the more something isn't right here. Surel, the rack is a toothed rod which engages with a a toothed gear wheel, which is controlled by the steering wheel. Turning the steering drives the rack left or right which changes the steering. As I understand it, these are normally lubricated and sealed for life. So what had corroded, what thread is being talked about and how did a catastrophic issue get resolved within five minutes me of kicking off?

The car is old and I am intending to move onto another vehicle - most likely a full electric, which unfortunately rules out another Toyota (the Prius has been the best car I've ever owned). My concern now is that this issue is on the car's Toyota record, affecting its value when I'm not entirely sure if there is an issue at all. I'd appreciate any insights!