In 2020, I drew from an HSA account from a previous employer opened prior to 2020. Last year (2020), IDK if my insurance was an HDHP or not. Was I covered by an "HDHP"??

Whether you were covered by an HDHP is only relevant while you are contributing to an HSA.  Answer the question according to when you were contributing to the HSA.  

Maintaining HDHP coverage throughout 2020 would also be relevant if you made an HSA contribution for 2019 under the last-month rule.  If you were covered by an HDHP plan for all of 2019, your contribution would not have been under the last-month rule and this wouldn't be a concern.

You must be covered by an eligible HDHP to make new contributions.  Once you have money in an HSA, you may spend it at any time for qualified medical expenses no matter what kind of insurance you have.  If you were not enrolled in a qualifying HDHP, it's ok to answer No, you were not covered.