A computing system receives from a media presentation device a query fingerprint stream representing media content being presented by the media presentation device, where the query fingerprint stream has been determined to represent a first channel. The computing system then detects that a threshold mismatch exists between the received query fingerprint stream and a reference fingerprint stream representing the first channel, thus indicating a likelihood that the media presentation device has transitioned from presenting the first channel to presenting a second channel. Responsive to detecting the threshold mismatch, the system thus discontinues channel-specific action with respect to the first channel. For instance, the system could discontinue superimposing of first-channel-specific content on the presented media content and perhaps start superimposing of second-channel-specific content instead.