Was there a clue to how Han and Chewie just happened to be in the same neighborhood as the Falcon as it was escaping Jakku? Was it just a coincidence? They were on a merchant mission to deliver Rathtars so its not like they were actively looking.
According to the novelization, they just happened to be in the same general vicinity.
Han explains that the Falcon had a beacon that turned on with the ship, and that they detected the beacon.
Looking away from them for the first time since they had emerged from below, their captor addressed his towering cohort. “Told ya we should’ve double-checked the Western Reaches! Just lucky we were in the general vicinity when the ship powered up and its beacon snapped on.”