No, they still own the stock, the government hasn’t taken anything from them. The stock might be worth less money the same way a house might be worth less money if a city government decided to stop repairing the road in front of it, or if the city relaxed zoning laws, but the price of assets in the market isn’t a responsibility of the government, and it generally does not incur liability when it causes them to change.
I think a more appropriate example would be if the government did some work around the house and in the process damaged the house, thereby lowering the value. The thing being damaged is shareholder confidence, which I thought (but IANAL) taps into different securities-related laws.
If the government damages physical property it is frequently liable for the cost of repairs, but to the extent that a share of Twitter stock represents something that can be damaged, that thing is Twitter itself. If through illegal meddling of some sort the government impaired Twitter’s ability to do business (say, for example, by flagrant targeted refusal to grant work visas), then the company or shareholders could have a cause to sue the government. The government is under no obligation to avoid impacting Twitter’s share price, especially as a side effect of some unrelated fully legitimate exercise of government power like auctioning off seized assets.
