United will try to re-route you on airlines of their choice or you can ask for a refund of the unused portion and flind your own way. At that point, it’s usually not cost-effective to buy a one-way ticket at short notice.

United, can (but you can’t force them to) decide to endorse you over to another carrier, but it’s rare. There’s definitely no policy to put a 1K on another carrier solely on the request or demand of that 1K.

Not sure why you think 1K is going to be treated special (long-time 1K here). Quit thinking that 1Ks might get special treatment and you’ll have less frustrations