Thanos’ home planet Titan is not the moon of Saturn of the same name, and its exact location in space is unclear.
Space is sort of, well, big and we have no idea exactly where Tony Stark is drifting in space.
Of course, it should be pointed out that, simply scanning the sky from the ground isn’t necessarily going to yield a lot of results by itself.
Whether we even have the ability to scan that far fast enough is unknown, and since nobody alive actually knows where Tony is, unless Nebula isn’t on the ship, nobody would even know where to start looking.
…
7 Major Things The Avengers: Endgame Trailer Taught Us