When someone limits foreign investment, they are not at all accomplishing their imagined goal of keeping domestic capital domestic. Instead, they are letting all these foreign investors take their money where it's valued, and therefore ruining any domestic companies' chances at success. Also, the domestic investors will take their money where businesses are doing successfully, which is not at home.
No, a cap on foreign investment does not limit the potential for fast capital flight. A person who wants to flee with their capital will find a way. It is unfair to seize money in any event, and a person who wants to withdraw their money and does so quickly will cause more disruption than a person who has foreign investments will cause by having their money overseas.