Pariah Planet by Murray Leinster

There were small scout-ships which came on ahead of the main fleet. They'd originally been guard-boats, intended for solar-system duty only and quite incapable of overdrive. They'd come from Weald in the cargo-holds of the liners now transformed into fighting ships. The scouts swept low, transmitting fine-screen images back to the fleet, of all that they might see before they were shot down. They found the landing-grid. It contained nothing larger than Calhoun's Med Ship, Aesclipus Twenty.

They searched here and there. They flitted to and fro, scanning wide bands of the surface of Dara. The planet's cities and highways and industrial centers were wholly open to inspection from the sky. It looked as if the scouts hunted most busily for the fleet of former grain-ships which Calhoun had said blueskins had seized and rushed away. If the scouts looked for them, they did not find them.