What about the option to recall your Explorers and Geos. On the condition that they return as long as they have been away, maybe. For example, if you sent specialist on his way 5 min ago and suddenly realize you would rather select a different search, it would take him 5 min to return as well.
Could also set a limit from which point you can no longer call them back (let's say they've traveled too far already to get your message about change of plans). It could be either a fixed time (like 10 min) or in correlation with the total search time, so more time to recall Explorers from a Long Search than Short Search.