If I understand correctly..,
You spot “what appears to be” an abandoned bike laying on someone’s front yard (in, under, or near some ‘other junk’). You go home to get you truck, return to the residence, ring the door bell, and determine that since no one answers the door (despite cars parked in the driveway) & by the placement/appearance of the bike... You determine that it is ‘most likely free to a good home’ and so took it home.
By the sound of things, you were probably right by your assumptions, but... I really do hope you left a note on the door with contact info in the possible event that you weren’t.