the fact that they did not claim you is irrelevant. the question is could they claim you. if they could clai you you don't get the stimulus. however, if your depency status changes where they can not claim you in 2020 you get the stimulus by filing your 2020 return
you could be claimed as a qualifying child (dependent) if all these tests are met
• you have the same principal abode as the other party for more than ½ the tax year. Temporary absences like for school are ignored
• If not a full-time student (5 months per year), under 19 at the end of the tax year. If a full-time student under 24 at end of the tax year.
• you haven't provided over ½ your own support
• you didn't file a joint return unless there was no tax liability but merely filing jointly to facilitate refund of taxes withheld or estimates paid
or as you could be a qualifying relative if all these tests are met
> your related or if not lived with the other party for the entire year
• your gross income for 2019 (2020) less than $4,200 ($4300)
• the other party provided over ½ his support
• you aren't a qualifying child of another taxpayer
