Useful to highlight this to United. Can OP confirm whether the meal vouchers had small print limiting their usage to certain menu items? Could OP theoretically have used this at another restaurant or was it limited to the hotel as part of a meal+room "package"?

Also, I'm curious as to whether these were issued on United BP cardstock or as separate SATS vouchers.

Unless specifically arranged, this does not seem to be reasonable practice. The issue with pursuing this matter is that it is less clear who the responsible party is -- I think it'll be helpful to raise this to United who may or may not provide an ETC to make things right.