There is a high concern about fraud when it comes to lost, stolen, or damaged visas. The State Department instructs people to re-apply for a new visa if their visa is damaged in any way.
Having a visa removed from your passport by someone else would likely qualify it as stolen, if not damaged (physical harm to the document which impairs its value). Stolen visas are supposed to be reported to the police and the consulate or embassy that issued the visa, according to the State Dept's FAQ webpage above.
Since there is no way to reinstate a previously issued visa in your passport after it is reported lost or stolen, and you have to apply for a new one, then it can be inferred that that visa is no longer valid. The consulate in HK referenced in the link above may not be the issuing consulate in your particular jurisdiction, but the information refers to U.S. visa regulations in general, which would apply to consulates and embassies all over the world.
