The goals of situated agents generally do not specify particular objects: they require only that some suitable object should be chosen and manipulated (e.g. any red block). Situated agents engaged in deictic reference grounding, however, may well track a chosen referent object with such fixity of purpose that an unchosen object may be regarded as an obstacle even though it satisfies the agent's goals. In earlier work this problem was bridged by hand-coding. This paper lifts the problem to the symbol level, endowing agents with perceptual referent selection actions and performing those actions as required to allow or disallow opportunistic re-selection of referents. Our work preserves the ability of situated agents to find and track specific objects, adds an ability to automatically exploit the opportunities allowed by nonspecific references, and provides a starting point for studying how much opportunistic perception is appropriate.