It's likely that the post-credits "Where's Fury?" scene is canon. I expect there was a much more elaborate "get to know you / debrief" scene that was intended to be part of Endgame, but it proved to be fairly dull and was cut for time.
Rocket absolutely knew "the morons" were going to Titan I, and would have mentioned this to Danvers. We know Danvers is pretty good at planetary surveying, so probably would've taken a pass around Titan. She would have found the fresh disturbance of a fight scene, and the landing feet impresson of the Benatar (and no ship) and possibly a puddle underneath it. Where did it go? Where would it have gone?
From that it's a matter of either following whatever trail a ship may leave (especially a damaged ship leaking stuff). Or simply guessing that they would make a beeline back to Earth, and following that path.
Or following a distress beacon - you have to figure if today's aircraft black boxes have a 30 day battery to power a sonar pinger, starship distress beacons have an independent power source too.
Also, Titan is hardly "not anything of significance", Thanos' homeworld matters. Tony was joking about the nearby 7-11's; I'm sure the franchise in that part of the galaxy is Circle-K.